02 said last night that due to the short turn-around between anouncement and release that it will not be offering pre-order on this phone.
However mobiles.co.uk are offering the first pre-orders for the 3GS. It promises dispatch on 18 June. Owned by carphone warehouse and offering a £60 Quidco for the pre-order, this is the hottest discount on the new darling.
You can use the £45/month tarriff and get more minutes and cut back to the £30/month tarriff after 9 months on 02.
Total costs (16GB)
18 months @ £30pcm=£713.82 (653.82 after Quidco)
9 months @£44pcm plus 9 months @ £30pcm=£747.98 (£687.98 after quidco)
32GB is £90 more.
(Calculations with VAT of 15%, it will go back up to 17.5% in December)
EDIT: note the attached voucher for a free bluetooth headset.