You knows guys, i'm getting seriously impressed with the coming warm spell.
1) The breakdown from the west just is not coming and even better, when the high shifts west the jet stream is still miles away and thickness values high so the worst case scenario is a thundery low. This point is alluded to by the chart below.
2) Temperatures are being vastly underdone by most people. Firstly uppers are as high as 9C which in June translates to 23-25C straight off, couple this with short nights and fairly dry ground in most places and its likely that the temperature will increase day by day. My personal belief is that we will breach 80F (probably north west London to Manchester, somewhere in that line), probably next weekend as humidity builds from the south and pressure relaxes slightly.