Hi there Damian,
If you have been in a debt management plan for over to years, then I would be fairly certain that your credit rating has been negatively effected. It is likely that one or more of your creditors has issued a default notice against you which will be registed on your file. As such, as Steve and Andrew have said, you should be able to take a mortgage but you will need to use a broker who can find you a lender who will work with you.
By the way, give that you currently have no property and nothing to loose, have you considered simply declaring yourself bankrupt to clear your debt? You would be debt free after 12 months. This might be better than looking at buying a property now and having the added strain on paying extra household bills which could mean paying less towards your debts and the dmp lasting even longer.....
Discharged from bankruptcy in 2010 and debt free. Thanks to all on this forum for your advice and support.