This isn't self catering but we did a break with baby to the Charlton House spa in Somerset and it was great! Spa was amazing and I thought good value. Lounge/bar had fires and lots of squashy sofas that my son climbed all over, monitor worked in the restaurant, food available all day including kid's menu, and great breakfast including buffet stuff for baby. We had to share a room but it was big, including a sofa area and big TV with cbeebies! The spa was definitely the best part. Indoor outdoor hydrotherapy pools with loads of jets, outdoor hot tub, sauna, steam room, etc, etc. They offer treatments too but you can use the pools as much as you like (not baby, but my husband and I took turns enjoying the spa).