Essex Ham suggest what to do if your amateur radio licence has lapsed and you're looking to return to the hobby
If your licence is no longer valid or has expired, you can’t use Ofcom’s online validation process to re-activate your licence and callsign. Instead, you have to complete an application form and post it to Ofcom to get your licence back. At the time of writing, there’s a fee of £20.
Read this Essex Ham article which shows the steps to take to getting back on the air - http://www.essexham.co.uk/reinstate-amateur-radio-licence
Amateur Radio Getting Started Guides - http://www.essexham.co.uk/getstarted
Essex Ham promoting amateur radio in Essex - http://www.essexham.co.uk/