I am currently winding up a narrowboat holiday in the UK. Two years ago we screwed up and went with Vodaphone. That was a big mistake. This year we were smarter and went with “Three”.
For 10 GBP I got a SIM with 1 gig data and 3000 texts and minutes for 30 days to use on my iPhone 6.
For 20 GBP i got a SIM for 12 gig data and 3000 texts and minutes for30 days to use on my iPad. Actually this SiM was intended for a phone, but works fine on my iPad. The iPad specific SIM would have been 40 GBP. The manager of the store that we visited recommended the phone SIM instead.
Both SIMs allow themselves to be used as a personal hotspot. The “Three” SIMs also work on the continent.
I recommend checking out “Three”.