Having broken a sele heres a few things I can advise based on my experience:
The engine *might* be worth £700 if its got service history and recent cambelt BUT not unless it can be heard running, once you've got it out then nobody is prepared to pay that much for an engine if they don't know if it works. Its a catch 22, I wanted to get on with it and get it stripped and off my drive, but if people want to hear a working engine you can't do that. I opted to buy GTV with dead engine and am going plant it into that
Probably worth stripping ancilleries off the engine, they are easy to sell and most people buying an engine don't need them.
The gearbox is worth very little but the actuator unit is worth good money, a few hundred quid. But you will need to be sure that it is the box that is broken not the selespeed unit.
You will not get £200 for leather IMHO, i've seen mint sets go for £150 on ebay. I guess if you get lucky and some1 is local you might.
Body panels are difficult to shift unless you can deliver, small items that you can box up and sell are much much easier.
I have made about £700 thus far, have perhaps £300 of parts left but I kept the engine and the leather, so its probably possible to get £1800 back but be prepared to store all the bits while you find buyers.