I personally use
http://www.honeybros.co.uk/ ,
http://www.buxtons.net/, although I'm not currently working in the arb field.
It may be worth giving a company such as the above a ring for advice, dependent on what you plan to do with the kit (i.e. what you need it for!) as there are a number of different options, gloves for example have different designs (mitt v glove), trousers come in 'classes' of protection (e.g. all round, front only) as well as being different in comfort/fit/performance (so are you an occasional user vs. a climber / all day ground user). Boots can be basic work type boots with protection, waterproof or not, hi-tech mountain type boots for remote foresters and climbers, wellies, and helmets range from the basic hard hat with a mesh visor and fitted muffs, to the full petzl Vertex job with chinstrap and no peak for climbing use.
Across all that lot the price varies massively too. Bear in mind that working on the end of a saw or feeding a chipper can be hot work, and some of the cheaper gear can be very bulky and sweaty!
However, above all, chainsaws and the trees we use them on can be very dangerous if not used and treated with the appropriate respect and skill - I don't mean that in a patronising way, just friendly concern for everyone reading!