'Raglan' is a possible answer although I thought that a Raglan is more a coat than a cardigan.
If this 'British places' quiz extends to the whole British Isles (??) then another possible answer might be (the Earl of)
Arran (
http://en.wikipedia.org/wiki/Earl_of_Arran">Wikipedia link). The Aran Islands off the west coast of Ireland have a
http://en.wikipedia.org/wiki/Aran_sweater">sweater named after them.
Maybe John d'A has thoughts on this?
JimC