dautarikanchha bro! transit visa chaidaina! I went to nepal via london this december and returned back same route..face no hastle at all...don't worry..u won't need it.But, london airport is quite hectic..b'coz of travelers queue and security natak.Make sure u carry a single handcarry with you. If u r carrying ur laptop with u...they want it out of ur handcarry or laptop case.Well,my point is nothing to worry about.London airport is as normal as other airports!! Have fun in nepal..with ur family,friends, and specially GF(s)....