Halfway stop London to Devon with kids

[MaggieMcSplash]

Hi
We are heading to South Molton in Devon tomorrow with two kids are two and four.
Does anyone know a good half way stop where they can run around for an hour or so have some food etc?
Thanks for all your help.

If you're National Trust or English Heritage members, pick a site!

Thanks bluechampagne we aren't national trust members but could look into it.

Dyrham Park is no more than 5 mins from junction 18 of the M4. There’s the Old Lodge picnic and play area to run free in, plus nature trails and a straw maze.

Oldbury Court Estate (junction 19) is registered parkland with woods and riverside paths. It has a play area centred on a water and sand play zone with a pirate play ship. You may need a towel and change of clothes! The play equipment for toddlers includes toddler swings, springy seesaw, springies, toddler spinner and embankment slide. Equipment for older children includes a dramatic rock feature with rope bridge, a slingshot, dish spinner, swings and zip wire. The whole play area includes lots of natural play features including logs, boulders, a woodland den area, picnic tables and plenty of open grass to run around on.