Mystery shopping?

I fancy giving mystery shopping a go. someone recommended grassroots to me. someone else know of any other agencies i could try?
Answer
You can approach the shops/companies head office yourself. some advertise on their websites. contact companies like signet (they own h. samuel, ernest jones, leslie davies) or arcadia (they own topshop, topbloke,etc.) with so blokey shops they are more likely to be looking for mystery shoppers all over the country