Hi to you both
The arm rest i have in my car is from an A4, same as the a3 one and also vw golf.
yes the only difference is the base plate but these only if my memory serves me correct cost about £17 And a fiver for the bolts.
cheap as chips.
And if like me the colour doesnt match your interior go to one of those fabric warehouses, match up some cloth and retrim it, it took me 20mins tops.
hope this helps