Sea to Summit Spark SP II bag. That whimpering you can hear is my wallet.
Its a lovely thing and only 545g in its stuffsac but I wonder if I'll warm to it, if you'll pardon the pun, the way I did to my Karrimor Xlite bag. Sure the Karrimor was only good to 11 degrees and weighed 787 or so but it was £40. £40 for a bag that tiny and light is stupendous value for money. Trouble is I froze my titzoff for one night in August 2015 when the temp got down to 5 degrees, hence the Spark.
So having rinsed my bank account severely, if you're ponding a camping trip from 29th July to 5th August I can pretty much guarantee there will be no cold nights from Kirkby Stephen up to Edinburgh. Looking at the weather forecast wet but not cold.