I do get the feeling that the data is no longer being actively maintained. They have stated it is down to when weather data is available and I believe the issue is that the weather data is no longer being generated regularly. It many respects I believe the reporting needs reworking so that the main graphs for the month that use generation figures are automatically generated and the weather related reporting is produced when it becomes available. I know that some of the information may be used by the national grid, some web sites such as grid watch quote the use of Sheffield uni solar research group, but I do wonder if the models completely use the information.
I have offered to lend a hand, but I believe the understanding is an undergrad or PhD student should do the work. Maybe the issue they are no longer going on to campus so do not maintain the system It is difficult to say.
I did speak on the train to one of the researchers and I did not get the impression things were going great for the maintenance of the site.
I use PV output for org as it does have some of the features of Sheffield solar and is pretty well automated.