Yes, the 215 was bought by Rover, and they used the engines in both the TR8 and some MGs. The main use, however was for the Rover automobiles and the Range Rover SUVs. The engines were increased in CI and fuel injection was added, and the engine is still in production! I read somewhere that the maximum CI on the same basic block is up to 5.1L now(over 300CI) - pretty amazing for an engine that was introduced in 1961 with 198CI! They have been a popular engine for aircraft due to their very light weight of 275 lb minus exhaust manifolds and starter. They are very reliable due to the use of cast-in-place cast iron cylinder liners. I heard that GM tried to buy the rights back for the engine when the gas crisis of the 70's came along, but Rover wouldn't sell.
On the subject of the door retainers, yes, you can easily change them yourself - the inner panel must be removed, or at least lifted, to get at the third screw, though. Larry Bible gave a good tip on finding the earlier year units - they are made a little stronger.