I think people on here need to take what is forecast with a glimmer of hope and with a pinch of salt. There will definately be heavy rain, that is a given. The thunder and lightning aspect may not be totally widespread and severe as the MetO think, but i GUARANTEE there will be embedded storms within that rain, i would say more towards coasts.
Last night, here in Aberdeenshire, i went to bed at 11pm, thought i heard distant thunder but shrugged it off. I then realised it was thunder as i heard it again. By 1130pm, i was in the car on the dual carriageway under about 1/2 foot of rain and CG lightning, turning the carriage way lights off (daylight sensors). In total we had about 20 strikes over 30 minutes then BOOM...GONE!
The moral of the story is that this storm popped up out of nothing, with no cape forcast for the area. If you have warm air coming up from France, with storms and very heavy rain, you can be damn sure there will be lightning for some...sometimes, it just happens no matter how much you stare at the computer screen or look out the window. I will look froward to the new thread on Sunday with all the storm reports!