I am surprised by the negative reviews as my experience of Allan Fuller could not have been more different. Back in 1996 they found us a house on the Dover House Estate/Conservation Area, under pretty unusual and urgent circumstances and they actually got us out of a pretty tight spot (chap called Michael).
15 years later we have had our house on sale with them again and I found them to be helpful, courteous, quick to respond to queries. They also moved up a gear again when we had put an offer in on a property, to try to get us an offer much sooner.
Don't believe the doubters - these agents are fine.