Mix of:
Local pop up trails (a couple at different shopping centres, a hospice one)
Cinema, although kids club/juniors has been crap this year, so only once for Cars 3.
National trust places
I've made a point of finding a different playground each week to visit - a new environment sparks interest in what is essentially the same old equipment.
Kids theatre - have been to 3 shows with another one coming up next week. Not particularly cheap, but mostly birthday outings, plus kids scheme at leisure centre have put on a couple relatively cheaply (£5 each to go, so cheaper than the cinema!)
Local ish garden centre has a nature trail/animal shelter attached, so we've been there a couple of times (annual pass, so essentially free as has been well used)
Library once a week to complete summer reading challenge.
We've also had 3 birthdays, so shopping for those plus baking and decorating cakes has filled a few days! And new toys means a couple of days of less whinging...
Plus legoland, and will go to Chessingron too (we have Merlin passes)
I am 6 weeks into summer holidays and beginning to flag a bit, but only 2 1/2 more weeks to go 