Didn't you say you could use your vouchers in JL ? Can you use their price-match facility when buying with vouchers ? If so, shop around for the best high st price first, and save a few bob !
Even if you don't get a price match, that set is £1488 inc. delivery at Dixons, and £1499 at JL, which includes their great 5 year warranty, surely worth it for the £11 difference
Or you could go for the package with that set and a DVD recorder for £50 more ?
Can't recommend JL highly enough (especially over DSG !)
Also, £200 isn't too bad an offer for your set, but I'd try for £250. £300 is maybe a bit steep, as you can get the new 32", with 3 yr warranty, for £399 if you know where to look (hope your mate doesn't read Hexus !)