A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,417
Are you sure that bags will be checked through on separate tickets? Not many airlines are still willing to do this.
Unless you're willing to buy new AMS-LON tickets at the airport, this doesn't seem like a good idea, although it's very likely to be fine if there are no delays the day you're traveling.
BTW, do you really care which London airport you use? Remember that if you're driving to the airport, you'll want to come and go from the same one. Otherwise, it's a matter of convenient/cheap transportation at the times you need.