You should be able to pick up a fast card for that sort of money easily enough here's how they compare:
http://www.tomshardware.co.uk/gaming-graphics-card-review,review-32899-7.html
A few pointers: Older cards need more power to get the job done, for a R9 280X/HD7970 the system will need a decent 600Watt powersupply with dual 6+2 pin PCI-E leads.
If you're on Amazon or Ebay check the sellers rep, the more positive feedback and the more units sold the better.
Manufacturer warranties don't usually transfer, check the sellers terms and conditions, reputable ones will offer at least a few days to allow for DOA parts.
Don't be tempted into a cheap R9 290 if it has the old reference single fan 'blower' cooler, a lot of them were used for bitcoin mining so the fan is probably worn out and those coolers were notoriously hot and noisy, even when new.
As a point of reference; With a little searching the R9 280 (formerly known as the HD7950 Boost Edition) can be found for a fraction under your £150 budget, brand new, full warranty: http://www.overclockers.co.uk/productlist.php?groupid=701&catid=56&subid=1842