DVLA and DVSA are both the same. In general they couldn't organise a (insert appropriate expletive) in a (insert appropriate location), although there can be exceptions if you happen to be lucky enough to deal with somebody who actually knows what they're doing.
No. Definitely not tapered. Also the PTFE tape I tried seemed to dissolve in the petrol. I've ordered some from another source. They seem from the photo to have a bigger hex., so I'll see if that makes a difference.