With alle the duties and CUSTOMS we get charged here in Europe, You will not be able to fight HK or US based sites, maybe european ones (which tend to be priced too high), but then You will not earn too much.
Try to get infos on Welch Allyn and Brightstar Systems (ballast + bulb + completed flashlights), the trailtech versions (especially the black one), Lupine Systems, maybe the Light and Motion lights as there is no source here in Europe for them, .....
Good luck
most might already have UK-importers, and there are not too many flashaholics around, without getting noted somehow, it will be very hard.