Any personal recommendations?

Medium-sized 'reluctant' model who will require a thorough de-tangle!  No scissoring required.

Indication of expected costs would be useful too.

Many thanks.

not my area sorry...but why not get all the required products and do the dog yourself....most groomers would charge extra to detangle  a long haired breed.
Plus if dog is that bad it may require clipping for the comfort of the dog ..its very painful for a long haired breed to remove knots.

I know of two nr Clevedon in North Somerset, one I've used and another recommended by a friend - is that near enough?  Let me know and I'll get details