Hi Simon.
I could help you with that, since I have done it recently. But I think Shirc put it on a plate for you...
Two observations if you can't find the Min19 seals at that supplier, Richard Banister has them. If you do not have practice changing the master cylinder seals, purchase a few more sets than you need, because it is easy to break one of the rubber seals when assembling it. If you think the master cylinders are too bad to recover, you also have them new or rebuilt at the usual dealers.