Planning a May trip & trying to figure out what we should buy in advance online - i.e. Eye tickets, Windsor Castle, etc. - downside is weather & locking in a specific date and time; upside is fast track passes or skipping the purchase ticket lines and saving time once there. There's a London Pass, two-for one- offers with a 7day tube pass purchased at a rail station, combo tickets, membership options, etc. Can anyone tell us about the crowds in May, how long lines are for getting tickets on site to Westminster Abbey, Tower of London, St. Paul's, Churchill's, Kensington Palace, etc.? We're trying to determine what we should secure and lock in advance of the trip and what we can wait on. We have our Evening theatre & concert tickets and Harry Potter tickets purchased and just need to figure out how best to avoid lines, crowds & maximize our time in London at the major sites.
I've never reserved ahead in London for anything except theater tickets and destination restaurants. Rick's London guidebook includes crowd-beating tips for each site, when needed, which mostly just indicate going early or late. For instance, pp. 276-7 mentions several places where you can buy Tower of London tickets in person with less line. You do save £1 if you buy tickets for the Tower of London and Kensington Palace online and the tickets allow one entry within a 7-day window, so that's quite flexible.
I'm in London now and it seems more crowded than ever before in May. Lines everywhere.