The lack of officially programed informal sessions in the evening is probably because the Chippenham Folk Festival organisers would prefer that folk attended the ticketed events........

This is probably understandable but it does not prevent folk from making their own arrangements with licensees etc. That an informal session appears in a programme and at certain times - does not alter the nature and the conventions of these events - which is really decided by those attending the sessions and those in charge of the venue - rather than the fesival organisers.

The other factor is that some pubs have their regular weekend night gigs. That was certainly the case with the Bar Reva - where there was a new (programmed) Extra Session held during the lunchtime peak but where continuation of this session into the evening - would not have been possible. Perhaps the Bar Reva would be prepared in future to hold (non-programmed) evening sessions? Although the acoustics in there were really poor and the music was easily drowned-out by the background noise from only the few afternoon drinkers and would only be worse on a full weekend night.

Also pubs do change over time and the 'poshing-up' of The Angel is a good example. This was used for all sorts of informal get-togethers and I am not sure that the loss of this venue in recent years - has really been replaced.