How about some Monitor Audio Radius 90's - £385 RRP (pair):
Shop for Monitor Audio RADIUS 90 Black Speaker Pair with Richer Sounds for a 6 Year Guarantee, expert advice and Lowest Prices Guaranteed
www.richersounds.com
and a Radius 225 as a centre - £305 RRP:
Shop for Monitor Audio RADIUS 225 Black Single Speaker with Richer Sounds for a 6 Year Guarantee, expert advice and Lowest Prices Guaranteed
www.richersounds.com
The 225 comes with keyhole mounting while 2 of these will mount the 90's - £15 each:
Shop for Monitor Audio MASM Black Single Speaker Wall Mount with Richer Sounds for expert advice and lowest prices guaranteed
www.richersounds.com
You can keep your QA rears. Then buy another pair of brackets and a set of Radius 45's for the rears (when funds allow?) - £219 RRP:
Shop for Monitor Audio RADIUS 45 Black Bookshelf Speaker Pair with Richer Sounds for a 6 Year Guarantee, expert advice and Lowest Prices Guaranteed
www.richersounds.com
Even if you bought all 5 speakers and 4x brackets, the total cost is £969 @ RRP - so under budget. I believe this will give a significant upgrade in sound quality, but as always recommend an audition or in home demo (ideally) before purchase.
Other option is keep the QA rears and get 3x Monitor Audio Apex 40's for LCR - £549 (each) RRP:
Shop for Monitor Audio Apex A40 (Black) Single Centre Speaker with Richer Sounds for a 6 Year Guarantee, expert advice and Lowest Prices Guaranteed
www.richersounds.com
This would be over your £1000 budget, but, you might get a discount if you haggle with dealers.
Here's a pic showing another forum members A40's in an LCR configuration:
Post in thread 'Monitor Audio Apex Owners Thread'
Monitor Audio Apex Owners Thread
Edit: You could even add 2 Apex 10's for rears - as they can be wall mounted - £329 (each):
Shop for Monitor Audio Apex A10 (Black) Single Speaker with Richer Sounds for a 6 Year Guarantee, expert advice and Lowest Prices Guaranteed
www.richersounds.com
I appreciate this blows your budget somewhat. But, I have some MA Silver 100's and the Apex range use the same drivers. So this will (imo) be a significant upgrade in sound quality over the QA's.