I've had this pump for a couple of years now. Th problems I have are the gauge works but is way out and it doesn't pump up presta valves.

Has anybody else had problems with this pump, I also notice that they have a lifetime warranty on their parts but since it's a US company I don't want to send it to the US. Has anybody ever had a replacement from Blackburn and can an individual send it to somewhere in the UK to be replaced or fixed

No experience with the tower pump but
Two years ago I had issues with the connections at the base of 'Blackburns' X6 lights which meant they either didn't work at all or would go off suddenly over rough stuff, returned to Blackburn rep via LBS & fixed free of charge under lifetime warranty.
Then not so long ago the waterproof switch on their Mars rear light that I have fell out ,this was also replaced under warranty.
NB. I'm in NZ, I didn't have a receipt for either item, and the X6 lights were 4 years old and bought in the UK. I got the impression it very much depends who the rep is

To take advantage of the lifetime warranty all you need to do is return it to the place of purchase and they will deal with the UK importer for you.