Hi, we'll be looking for a picnic site near Junction 17 of the M4. Can't really afford service station food at Leigh Delamere and would kind of rather not try and picnic there as have started to loathe them all. Any local tips for somewhere nice to go within 10 mins or so of the motorway?
Do you want somewhere literally just for a picnic and then go, or for a longer stop-off?
If it's a quick picnic, I would head into Chippenham and go to one of the parks there. Monkton Park is right in the middle of town, river running through the park, small children's play area etc. Also John Coles Park, this is a nicer park and also has play area, picnic benches etc. Loads of space for children to run around, kick a ball around or whatever.
If you want a longer stop-off/visit to somewhere, you could head to Bowood House which is a stately home/gardens/adventure playground, but you do have to pay for that and would need to spend a couple of hours there to make it worth your while.