Found some 635 on eBay just life expired. Can't believe the full price!!!
The price for the 50ml bottle isn't that bad and assuming it has similar lifetimes to the 638 you will still have it for the next time around for "Wheel Bearings Part II"
In fact I might just pick up another bottle of the 638 at the prices they're selling at because I seem to remember being greatly impressed at the cost of the stuff back in the 80s, so anything under £25 sounds very cheap.
JB is right, the 638 is a faster set but not ridiculously so. Truthfully I don't know if it is the 5 minutes claimed or not because I've never yet dismantled the hub once I've applied Loctite and bolted it up. Well, not until the bearings are on the way out anyway, which is usually a few years later. I use the same stuff on the Elan's wheel bearings because the housing is a bit worn and the gap filling properties work fine. But you do need a blowlamp to get it apart, it sticks very well.
Brian
Actually the more I think about it, I'm going to buy one of their 638's..... thanks for that Ebay Idea.