If this is your area - http://intersoundguitars.co.uk/ Intersound Dursley Gloucestershire. I find them most engaging. We only use them to put Stroud Ceilidhs poster up and the odd purchase of strings for friends' "thankyou" gifts. They don't seem too pushy but are working musicians locally. They carry at least 4 left-hand acoustics (didn't count the electrics).
Best is a nebulous term but I rate quality of service, knowledge, and personality as far more important than numbers, though choice must be attractive. They have a lot of choice.
One I would soundly NOT recommend is World Guitars in Stonehouse Gloucs. Mostly electric guitars and the owner had that air of superiority when I spoke to him. Others I have sent his way regard him as a name dropper. More ready to tell you who he knows than talk guitars. And that came from a guy whose son is in an internationally successful heavy metal band and has guitars coming out of his ears and knows a lot of those "names". Both were unimpressed.