Nice pics! 89BA82 was an ARV in earlier days judging by the fixings on the glacier plate, one for the rarely used crane jib, and the square section for the pushing block. It could have been used a a "wedge" ie a turretless driver training vehicle. 00SP37 was also an ARV/wedge or both could have been tugs used on gunnery ranges.
It may be of interest that about 10 years ago I finished a Centurion register, and located, (I didn't see all of them!), just over 100 Centurions at various locations in the UK. Some were runners, some definitely were not! Three were at Manby as I recall, the two above and 04ZR 89. Information suggests all three came from DERA Shoeburyness Gunnery trials unit, now long gone, which suggests they were all tugs.