As I said, enhanced propagation conditions could be giving you signals from transmitters which you would not normally receive, so it is no real surprise. They could come and go over a matter of minutes as conditions change.
That is an interesting range of channel numbers, and is from at least two transmitters probably Whitehawk Hill and Rowridge (Isle of Wight). One, 44, is a bit of a mystery however.
The full range of channels for Rowridge and Whitehawk are:
Rowridge: 24, 27, 21, 25, 22, 28
Whitehawk: 60, 53, 51, 57, 56, 48
There are several of the Whitehawk relays which use 44, so it could be one of them.
If you are interested in studying the channel numbers in more detail, you can find the full list for the Meridian region
here. But don't forget that only about half of the Meridian transmitter groups have changed so far.
If you should think you are getting anything from outside the Meridian region then the other documents can be selected from
here (unless it happened to be French of course, which on the S. Coast is possible).