It really does sound a bit ridiculous. But thanks for the tips!

I did the whole shebang. Have just preordered it. Went through Topcashback, applied all 3 promo codes. Current order with nokia stands at £306.45.

Nothing shown up in Topcashback yet. Here's to hoping it works out to £256.46!

Edit: Ok, Topcashback now showing £49.90 pending for me as well.