[user104658]

It sounds like this is mainly a London problem and (from having briefly attempted to drive in London) I'm pretty sure it'll be because traffic in London, at certain times of day, simply does not move. I mean Edinburgh can be bad at times but ... it's a whole other level. We drove from Scotland, got to the outskirts of London at the expected time (actually nearly 30 mins early) ... Pulled into the hotel car park two HOURS later than expected after crawling through the city at 3mph. Torture.