Hi Patricia, welcome to the forum.

Short term rental homes in the Orlando / Kissimmee area need to be licenced and are zoned as such. There are very few (if any) such zones close to International Drive and Universal although there are a large number of hotels and suites in that area. Most of the pool villas and townhomes are situated closer to Disney (along the US192 and SR27 highways).
I think that one of the dificult things for UK guests to grasp initially, is the size of the area. Wherever you want to travel to , whether to Disney, Universal, Seaworld or the shopping malls will often entail 15 to 40 mins driving. (If you're very close to Disney or Universal, it will still be a fair distance from the other attractions).
As Julie says - best course of action is to decide what type of accommodation will suit your family best (pool villa /townhouse/hotel or room suite) and then look at areas.
Both the 192/27 and I/Drive are roughly the same travelling times from Sanford (as you would take different access roads, some of which are not as busy!)
If you have any questions at all about the accommodation or any other aspect of the holiday, ask away - or use the "Search" facility on the forum.
Happy hunting! [msnsmile2]