Oshkosh George: Actually surprised me--- From the BA website----
9-16 OCt £420
BUT!
27 Sep--1 OCT £1247!!!!
The latter price is, in part, because there is no Saturday night stay, so the lower fares aren't valid. Also 27 September is very busy outbound so only the top fare is available.
So 29 Sep - 1 Oct (which also doesn't include a Saturday night) is also £1427, but 29 Sep - 2 Oct (which does include a Saturday night) is therefore £505.