Not much, I'm afraid.
Fastest recorded on tandem: 46.2, Glen Convinth, Highland. I think we may have exceeded this the day after I'd lost the computer, descending from the Cross of Greet towards High Bentham. It was screamingly fast.
Fastest in Essex on tandem: 45.2, Essex Way, South Benfleet.
Fastest on solo machine: 44.something, going towards Wantage on last year's Anfractuous.