When I arrive in Moscow I have some fees owed for rent and such. As such I need to bring a reasonable amount of cash with me. I was about to order a lot of roubles and some GBP for my layover-quick-tour of London. But I did a quick Google conversion and see that my bank is using a horrible rate, it is going to cost me about $150-$200 more than the conversion rate Google (and other sites) are reporting.

But, there is no transfer fee. If I exchange at the airport, I assume I will get the better rates, but is there a limit on how much I can exchange, and are there fees? Heathrow has a converter, and they seem to be using the better rates, but, they mention fees are a downside to exchanging at airports- but they do not mention their fees.

I think 250USD in GBP might be a lot for 14 hours- but I have a short amount of time to see the city, and do not want to get stuck trying to figure out how to pay for an expensive cab ride tour or something .

Thanks, I have only flown international once, and that was just tourist dollars nothing this significant- so this is new territory.