It seems that. as I feared. the PHP changes on my site by my host are going to be implemented by the end of March (so I'm presuming it's today!). Robin is very kindly working on this for me but as the coding is so old, it is quite a massive job so is likely to take a while. Not sure whether the site will be left in a working state or not.
If you find any problems with anything on the site, please do let me know and I'll pass the information on to Robin. (If PMs aren't working, please use my email email@example.com).