HSBC also says it takes 6-8 weeks, but it doesn't always. I've been depositing loan checks for the last couple years and sometimes it takes a week or two, sometimes indeed six weeks. I talked to a guy at my branch once and he said sometimes it depends on the status of your account -- if you already have a decent amount of money in your account, they will deposit the funds sooner (before they arrive from the US) knowing they can get some money back if the check bounces or something. But I don't think this is true because I have never had a lot of money in my account when I deposited my checks, and the time to clear still varies by a lot.
Anyway, I agree it's BS. From my own experience, I think UK banks are way behind the US when it comes to customer service and timeliness, not just on this but lots of other things.