I did all the restoration work required on my particular Saracen, myself with my (now, sadly departed) father watching as I
removed the engine using a forklift to replace the Fluid Flywheel, then I had a mate help me to shove the engine back onto the transmission, after having done the flywheel.
I had new rigid hydraulic pipes made up to replace the rusted-out ones under the floor/transmission.
I had to cut open the fuel tank, to make some repairs where it was rusted. Following this was a complete bare-metal repaint, brake overhaul, followed by some running/adjusting of the gearchange mechanism.... That was likely the most mind-numbing part as it has to be driven, to warm the transmission up, then adjust the 'throw' of a link rod connected to the gear change pedal, to ensure the internal mechanism works correctly. It now drives beautifully, and has done for over 1000 miles.
Referring to your other points, a 'steal' would be anything from £0... Since even scrap they are worth a fair bit, but it is SUCH a shame when these fine vehicles are scrapped, since even a 'range-wreck' can provide much needed parts to keep others going.
A scruffy one which runs/drives/stops is worth more than one that's simply tarted-up with a fresh paint job, sometimes done to draw the customers eye from a myriad of annoyingly awkward faults to attend to.
Generally due to the physical size of them they tend to be stored outside, unless the owner is lucky enough to own a big enough shed.... Saracens are NOT water-tight, and if stored outside, uncovered they will let rainwater dribble in through where the turret top-hatch hinge is... Causing ugly rusty streaky stains to appear inside on the usually silver-painted interior...As for oil-leaks, pretty much every armoured vehicle of this era tend to 'leave their mark', where parked, also the engines oil-breather pipe exits down the side of the engine, about 4-5 " off the engine-bay floor... an oily film will naturally build up on the hull floor, and if left indefinitely will eventually form a slick of oil sloshing around in the hull.... In the base of the hull there are several access points to drain oil from various internal components, so any surplus oil will likely drip from these. Normal practice is to periodically swill-out the majority of this so as not to leak oil every time it's driven... Personally I leave my access panels off, and it allows virtually all oily deposits/rainwater to drain away safely.
The Rolls Royce B Series engines were designed not long after the end of WWII, so are of the type that wer designed to consume/use a little of their oil in normal running, if all the oil seals are in good condition, oil loss is fairly minimal, dependant on mileage. The vehicles will deteriorate if not used, as seals dry-out, or get used to being in one position, then when used after a long period of storage will start to leak, sometimes catastrophically, as happened to my fluid-flywheel main seal.... No amount of leak-stopper fluid will sort this as the pressure in it when operating is so high...so it's quite an involved job to sort that particular nightmare out... The engine is almost half a ton by itself, and the armoured radiator grill and top-plates are not exactly light either....
As for prices, well, its a buyers market, if a buyer is really set on one, they'll usually pay whatever the asking price is, but generally a scruffy runner with no mechanical faults you are likely looking at between £4k and £6.5k depending on its 'completeness', -sometimes things like headlights, light fittings, the horn, (oddly VERY expensive to buy and difficult to find cheap....-I've just found one after looking for 9 years!!!, I found one for £8.00, but have seen them sold for £258.00!!!!!, yet you can buy a pair of rear doors for £180!!
An immaculate runner, all up together, road registered, fully serviced ,complete with all its C.E.S. and radios etc would likely change hands for £9.5k +
Once you have one, it's still not all plain-sailing.... Maintenance is quite full-on, and physically demanding.... For example every 5-6000 miles the circumference of the tyres must be measured, compared, and the wheels swapped about to even out the wear, sometimes even between two or more similar vehicles!,... The front and centre tyres wear quite quickly!, especially if you do a lot of Tarmac-miles, not so bad if it's raining, as it allows a little bit of 'give', as there's only one differential, so transmission 'wind-up' can cause problems... They need a bit of loose/dirt running fairly frequently....
The thirst for petrol is in the region of up to 3 mpg off-road, around town etc about 4-5mpg, while on a decent run, where you can get momentum on your side you CAN get 8-9, MAYBE even 10mpg if all your roads are flat.....
the other problem is the tyres again.... They are VERY hard to find here in the UK, as Dunlop sold the moulds to Simex Tyres, who, while the can produce new ones, they won't sell to EU countries as the tyres are not 'E' marked.
Useable tyres here, when they do turn up are £350 +, new £500+..... and you can't just put one new tyre on, for reasons already mentioned above.... (I was unbelievably lucky and won a full set, on wheels, on eBay for £650...-mainly because someone spelt 'saracen' wrong as far as I can make out, as I was the only bidder!)
let eat me know if you want me to look at this 'Telford' one or any others...- as I said I'm going to look at another one needing some work in London very soon, too.
Hopefully some of the above is some help to you