You are right about the tough part being to move them on. Fortunately I don't need to move them on, because as totally refurbished places they are fairly easy to rent.
Yet again I found a very solid and trustworthy estate agent (must be in the Guiness book of records as the only one) in the town - an independent running a site called
http://www.rentaunit.co.uk. Seeing as I'm buying at auction and getting refurb at good prices I can make 10-15% annual.
I would far far rather do this than put money in a bank where they'll give me 3% and then lend out 10x the deposit to people on 25% credit cards.