I bought ZOTAC 780 TI from scan a week ago it was £440 (£420 but P&P is expensive). This card will cost you exactly £400 now. Really happy I purchased it, because my ZOTAC in SLI works well, and in addition SLI 780 TI will perform better than 980. If you can't afford SLI just get a single GPU, it clocks at 1071 (checked in GPU-Z) even though the core clock says 941. Differences aren't going to be huge.
If the difference between 980 and 780 TI isn't going to be huge, then the prices will improve which means that some people will miss great opportunities. Also, when 980 comes out it will be expensive, and if the card is good and will slightly top 780 TI, then the price will stay up for quite some time.
If you look carefully at the scan website, all other 780 TI's are way more expensive. At least £80-100. ZOTAC gives you 5 year warranty, therefore it's worth getting it. Something happens to it, then you can replace it (I doubt if anything will happen to it if you'll treat it well). Moreover, customer support is very helpful and fast.
Prices of 780 (NOT TI) are very similar to ZOTAC 780 TI, so just let that sink in....
EDIT: I checked and scan has the cheapest ZOTAC 780 TI OC card on the web. Everywhere else it's about £470, so I'd hurry up and get another one. If I manage to get more money, I'm doing 3-way SLI and this build will last for years.