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.
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.