I think a lot of them places are staffed by non-cyclists and just regular joes trying to make a living. Like some retail electrical shops now. There are some amazing bike shops here in Ireland and some that I would refuse to go into because like that, they are manned by people that are just there to work and get paid. I would rather take the chance online and get a bike than go into one of these shops. Alternatively ask some local riders where they go. A cyclist will always know a good place to shop in or get work done in.
There is a lot you can do now to enable you to get a bike online. The price might be worth it. There are excellent fitting guides out there which should get you in the ball park of a nice fit.
British Cycling Fitting
Peter Whites Fitting Guide