Then the results came out and they'd given me the wrong time, by about 40 seconds. No idea what happened so I emailed them. Got told the results were right, told them they weren't, then then admitted they were wrong and gave me a new official time. Still nowhere near what I ran, but closer than what they'd originally published. I asked what the actual issue had been, but they wouldn't tell me.
It was the same organisers (using the term loosely) that put on the Blackpool Marathon, so I think I'll be giving them a big swerve in future. Good job it was only a half marathon or I'd have been annoyed.