julia garrett normally has a big range of saddles, there's chris puddy and also jennys tack shop.
i suppose it depends on where abouts in somerset you are as to who will travel there.
Murphy's is in North Somerset (Hewish about 5 minutes off the Weston junction of the M5) - they usually have a decent selection and definately stock Kent and Masters although not having looked for a while not sure if they carry the other 2.