I am under the impression that I will have to take the General Skills Test that was required for issue of the PPL.
NO! The initial Issue PPL Skill test is only ever used for initial issue. The Skill Test that you take for Renewal of an expired rating is exactly the same as the Proficiency Check that you take to revalidate a current one. There is a navigation section that is at the discretion of the examiner and will simply determine that you can still navigate; if you have lapsed for a long time the examiner may require you to do a little more.
The content of the test is here:
http://www.caa.co.uk/docs/33/FORSRG1157.pdf