I remember when i used to be an audio fitter many years ago, there were ISO adaptors that you are supposed to use when fitting aftermarket stereos to VW, audi, seat, skoda etc. From what i can remember they just sent the permanent live to both the switched and permanent input on the head unit, and moved the blue wire(remote/aerial) to a different pin.

Using any aftermarket head unit that doesn't have ISO direct into the unit should allow one to swap the wires around themselfes, that's what i used to do anyway.

Am i missing anything?

Think i did a few fabias and they needed aerial amps fitting to get decent FM reception, is this also true?

So i just lob the old stereo out, fit fascia adaptor, set wiring for permanent 12v to head unit, fit aerial booster, chuck the head unit it and bobs yer uncle?

yep should be it mate.

youll need to swap red and yellow if the headunit is losing memory.

and you will need a signal booster which taps into a remote feed off the headunit.

I used an iso adaptor, cost about £3 and saves pulling wires etc, also allowed me to cut wires and connect to to my front speakers from the amp without running new wire to the doors

Good stuff cheers