I don't know anything about customessays.co.uk but I have been to Sheffield many times and the address they have stated (124 BLAIR ATHOL ROAD) is a residential address off ecclesall road. This not a good sign as it suggests it is being run from a bedroom. If you have google earth you can check this or if you have a friend in Sheffield you can ask them to check. Also a 3000 word essay costs just £168. This should ring further alarm bells. Don't compromise, just take your time and keep looking