Thanks Tony this is helpful.
I did submit a tax return for 2012/13 and I did state in that my self employment ended in October 2012 or thereabouts. Nevertheless they are still asking for payment for this year. I wonder if they have made a mistake?
I think I will call them as you suggest. When I call them should I mention the rent a room scheme and my lodgers' self employment or is it best not to complicate things?
I have just spoken with HMRC and they are doing as you say- reducing payments on account to zero for this year but keeping me on the self assessment system because they asked a long list of questions including about rental income so I needed to declare that, and on basis of current forecasts I will be over the threshold for the scheme next year. They asked if the room was rented "for residential purposes only" to which I said yes.
Do I now need to stipulate anything to my lodger about what he claims back as expenses in terms of his self employment? For example, he may be thinking about claiming rent and bills as 'business expenses.'