Den, there are mystery shopper forums in the UK that could probably be of much greater help to you. Most of us are from the US and Canada and while some of the companies we shop, such as Gapbuster and Bare International, do shops in other parts of the world, we really don't see them much. Let me suggest you Google "Mystery Shop Forums UK" and try some of the ones there. Members of such forums will be familiar who shops in the area. I tried a search on Jobslinger.com for the UK and it returned only one shop through Beyond Hello so I suspect that Jobslinger would not be a particularly useful tool for you.