Nothing dodgy, you just need the £50 off of £500 voucher with O2 moments (you can just pick up a cheapy Pay As You Go SIM in order to qualify to use this if you're not on O2) and a little bit of time.
1 - buy the iPad Air 2 64GB for £479 and the Apple USB Lightning adapter for £25, coming to £505 total
2 - use voucher to bring down to £455
3 - then, in a separate transaction, just return the unopened adapter and be credited £25 back to your card, therefore paying £430 for a 64GB iPad Air 2, no fuss, no rules broken.
Did this myself, there were no issues as you're not breaking any terms.