Unfortunately I don't know a breeder in Stafford however if your struggling I would suggest approaching your local vets, who should know of pet breeders in Stafford and should be able to point you towards someone local and reputable.
There is a discussion already on the forum for good vets however my recommendation would be to make a quick phone call to Park House Vets on the Wolverhampton Road
I don't all all mean to be rude or presumptive but this weekend is a very short time frame - have you considered all of the implications and responsibilities of owing guinea pigs?