Well I'll take the liberty of replying to my own question, since I am just back from Guam - in the hope it might be of use if anyone considers a trip. Posting this in Zen Divers since Guam seems like a Japanese city at times, apparantly 70% of the tourists are Japanese and it seemed like 95% at my hotel!
I stayed with Fiesta Resort, which was pretty fine. Nice rooms, comfortable beds and good location right on the bay and within a few minutes walk of some good restaurants. $90 a night
Fiesta Resort Guam
For diving, it came down to a choice between
MICRONESIAN DIVERS ASSN - GUAM & PACIFIC MICRONESIA SCUBA DIVING
WELCOME TO LET'S DIVE GUAM! We hope you enjoy our website. English & Japanese text.
MDA is cheaper, but don't do hotel pickups or offer guides. I opted for Lets Dive Guam, 2 morning boat dives for $105 and they were good - everything ran like clockwork timewise and the guides were helpful informative and found critters underwater. Chris & his wife both speak fluent Japanese too for any Japanese divers.
Diving is ok, the water is 30 degrees's and the visibility superb but I was a little dissappointed with the lack of marine life and there are no lush flowing soft coral beds here... rocks and a few hard corals are the order of the day. Nevertheless it's still a good place to do a few relaxed dives.. here are a few pictures I took.
A young dragon wrasse - a PITA to photograph as it seemed to be on speed! (hence the lack of precise focus!)
Some pretty filefish (I think, can anyone ID the species?)
Blue striped sleeper gobies
An as yet unidentified nudibranch
The famous blue hole dive