Repairs to overdrive gearbox!

I've had an overdrive issue lately with the Brown estate. The overdrive works fine when cold, but wont kick in when the car's warmed up.

A few people suggested it could be the valves and filter in the overdrive sump clogged up, so I removed them and cleaned them all out. I also managed to destroy the gasket while I was taking off the sump so I need to order one of these on Monday. I also robbed a solenoid switch off of another gearbox I had laying around as I strongly suspect this could be the issue as well.

I'm now considering using this car for the Round Britain run in October instead of the rally car, (More room to sleep in the back of it!) so I need to get all of the outstanding issues sorted.

Other jobs consist of: Changing the pedal box, (It was converted from an auto set up to manual, but they didn't use spacer bushes, so the pedals are wobbly!) fixing the handbrake which is non-existent on the off side, finding out where the 'knock' is coming from on the offside front whenever we hit a pot hole or bump up a kerb, and maybe fit power steering. 2000 miles in a weekend with no power steering is just not funny!