Thanks for responding to my question
Yes it was not allowed to have a lodger in the tenancy agreement.
How can I get my property back? - You need to write and ask that he vacate it within 28 days else you will issue proceedings and seek costs against him. If he refuses then you need to issue a County Court claim for possession. You can do this either online at: https://www.possessionclaim.gov.uk/pcol or by completing form N5 http://hmctscourtfinder.justice.gov.uk/courtfinder/forms/n005-eng.pdf and taking it to your local County Court. There will then be a hearing which you should attend and a Judge will consider whether to grant possession. If you do a date will be given for the lodger to leave. If they do not then you can apply for a warrant of eviction which will send the bailiffs in.
If this fully resolves your question then please take a moment before you leave and rate my service, it only takes a second and is an important part of the process. Otherwise if you need more information or help then please click reply. Alex