Most any of the new respirators are good. Manufacturers include MSA (Mine Safety Appliances), 3M, North, Survivair, etc. Most make good, comfortable silicone rubber devices.
Get yourself a 1/2 mask air purifying respirator (APR) with either organic cartridges + a paint prefilter (a separate piece mounted on the cartridge utilizing a re-usable holder), or a combination cartridge equipped with an organic vapor and N95 filter (They will be color-coded black and pink). Most home improvement stores have them on the shelves, usually as a ready-to-go package deal--respirator and cartridges.
If you are indeed across the pond, check out this link to locate respiratory protection:
http://www.kellysearch.co.uk/gb-product-77920.html
Lab Safety here in the U.S. is an excellent source for a variety of respirators: www.labsafety.com
Please keep in mind that the color coding and N95 designations are a part of U.S. approvals, which is handled primarily by the National Institute for Occupational Safety and Health (NIOSH). Regulations, color-coding (if any), and designations may be different in the UK.
Good luck in your search. One last bit of advice: Don't buy respirators off of Ebay. I have observed too many sellers selling stuff that has no apparent approval (NIOSH, MSHA, etc.). Buy locally, or from a recognised manufacurer/distributor.
Hope this helps.
Gip Winecoff