Many thanks for all the replies so far.
I am not about to commence serious IFR flying but would like to be able to fly on instruments in cloud if the weather deteriorates and also navigate using NDBs and VORs more effectively than I am currently able. I repeat, I fly on an NPPL licence, I'm not a budding airline pilot - maybe 40 year's ago!
I would also like to be able to fly an approach on instruments in extremis. I realise that this would possible be illegal but I would prefer to argue this on the ground afterwards, rather than to explain at the pearly gates that I could have saved myself but the rules didn't allow it.
This may be a Bad Idea. I'm sure someone will put me right!