Hi i am looking to upgrade my boring  seats to st half leather, or titanium full leather, my questions  are 

1/ will mk2 seats fit, a mk3 ? 

2/ if electric adjustable is wiring loom pre installed, with  just  a case of plug and play with maybe an additional relay?

3/ are all seat air bags wired same in looms in car?

4/ will 2015 on model seats fit mk3?

Many thanks 

1) - I believe they may well fit, but, I am uncertain of the rails being different in width, if they are not you could remove the runners from the donor vehicle

2) - Some may require a relay, others may require the GEM board software changing with something like ELMCONFIG to allow you to enable the software switches. Also of course, you would need to install the additional switches where necessary.

3) - Seat airbag wiring may differ between models, so always best to consult a wiring diagram

4) - Refer to the above :)