Sadly GTI's dont break for a lot of cash (ive done 2) due 2 the fact that there arnt many parts which are unique 2 the gti and the engines dont tend 2 sell fast or for alot of money
Between the two ive done this is what i recon u would get for the parts
interior (1) £150 leather £300
wheels £150-£200 depending on condiction
engine+ ecu, wirring £150-£200
gearbox £100-£150
gti bits (eg splitter, rear spoiler (but sadly u dont normaly find that both these have servived), gear knob, fogs, steering wheel)
£100-£150
Thats only £600-£700 quid and your left with all the normal polo stuff that ither doesnt sell or takes ages 2 sell.
U proberly could get more but would mean holding on 2 bits and hoping 2 get lucky!
I personal have paid £600 twice for crash GTI's (and would again) but the only reason i do it is so when all those bits are sold off he car owes me nothing or close 2 nothing! i then keep what ever is left in my (stores) for spares for my car or 2 be able 2 offer my customers cheep second hand parts.