You do not legally need to do the r/t test before flying - you just can't use the radio, which is a bit impractical at most airfields! If you have not done anything about it (i.e. revalidated by experience/signature) your SEP rating is out of date and will need revalidating by test (not cash to the CAA just aircraft and examiner costs), you could probably get the r/t and flight test done at the same time. There may be a way of getting your r/t licence based on your RAF experience but this is not an area I know.
