Before anyone draws too many conclusions, I should say I abhor the heat and
humidity of summer, much preferring the cooler half of the year.

However, the GFS run has been remarkably consistant (considering the range)
of late. It's been showing high pressure moving northwards next weekend,
bringing hot air over the UK and today's 06z run is no exception.

The ensembles show an amazing degree of confidence this far out:

http://www.wetter-zentrale.de/pics/MT8_London_ens.gif

....so as a hot weather hater I'll hope they're wrong :P