Don't delay taking your theory test, it should be one of the first things you consider doing. The theory test is currently valid for 2 years. You are probably aware that there is a backlog for tests and waiting times especially at Telford are very long. However there are tests available at other test centres and cancellations are frequently available at Telford. I can advise you booking your test.
Only book your theory and practical tests on the offical gov.uk website. There are plenty of official looking websites that will charge a handling fee to book the test on your behalf. You should not currently pay anymore than £25 for your theory test and £62 for the practical test.