SRG2138 is for the examiner's record submission - not the licence holder.
Also, SRG1173C (which you say was completed) is for a rating RENEWAL - not a REVALIDATION. If, indeed, you required a RENEWAL then the assessment, training and testing for that needs to have been done by an ATO. For a revalidation, the form is SRG1773B:
http://www.caa.co.uk/docs/33/SRG1173Benabled.pdf
More guidance in 1173E:
http://www.caa.co.uk/docs/33/SRG1173Eenabled.pdf