This could be coincidence, but I got an email from Amazon this morning with Vita 2000 consoles down to £139. That's down from £169 last week, although the price has fluctuated up and down over the months. That comes on the heels of US sites and stores reducing the prices of PS TV and Vita memory cards.
Game also has it at £129, and I'm sure the few other places that still sell the Vita will be adjusting things soon. So, while there's no particular guarantee of an E3 price cut, it looks like stores are trying to sell them while they can, before any official price cut, perhaps to £109 or £119, kicks in next week. With most games in the catalogue now between £10-15 for boxed copies or regularly on sale on PSN, the Vita is becoming quite the gaming bargain.
Also, note the 64GB import memory card is only a little more than the official 32GB card, if you can afford it, you'd be mad not to pick one up.