When DD was a toddler, we got her a Trespass baby fleece suit with a hood and flip over hands and feet and it was fantastic for camping. It was better than most fleece suits because in the mornings you could flip up the feet and she could wear wellies round the site. Also the hood was great if it was cold at night as she didn't like wearing a hat in bed.
The Trespass one seems not to be available any more, but I found the Sprayway lamb suit on Go Outdoors today and it seems even more useful as it has poppers round the legs so you can change a nappy without having to remove the suit.
It is a bit pricey but worth considering for an older baby/toddler: www.gooutdoors.co.uk/sprayway-lamb-suit-p273597