Things have gone very quiet on the mobile callthrough front, but this is because networks have disallowed calls from their inclusive minutes, not than previous services have disappeared.
There are still services operating on 07744, 07755, 0797300 etc. - its just that we can't connect to them economically !
However, I got a report from korny88 this morning ( and he would have posted this himself if he had sufficient internet access ) that he had made some tests using a Blyke SIM.
Although it wouldn't allow calls to a 07744 number, it DID connect him to a number in the 0787300 range.
My information is that this range no longer belongs to the original 0787300 company - as they disconnected from the range holder (Routo) a while ago.
However there are other companies now using this number range.
Orange still allows calls to these numbers, but they charge a premium price alas.
So the Blyke SIM is the first one that I have come across that still connects there.
It may not be a big 'window of opportunity' - but its good to know that there is still one on offer anyway !