The500man
The definitions from CAP804, Part B
http://www.caa.co.uk/docs/33/CAP804Cor.pdf are;
Renewal (of a licence, rating or certificate)
The administrative action taken after a licence, rating or certificate has lapsed for the purpose of renewing the privileges of the licence, rating or certificate for a further specified period consequent upon the fulfilment of specified requirements.
Revalidation (of a licence, rating or certificate)
The administrative action taken within the period of validity of a licence, rating or certificate which allows the holder to continue to exercise the privileges of a rating or certificate for a further specified period consequent upon the fulfilment of specified requirements.
Currently, until 17th September;
If you revalidate a SEP(L) class rating, either by experience or LPC, then the examiner can make the licence entry. The SRG 1119 does need to be completed and sent to the CAA, the form does kind of imply it should be accompanied by a SRG 1187, payment form, but it's not required in these circumstances.
If you renew, which requires a LST, if the rating has been expired by less than 5 years, then it's the same as above. All administration done by the examiner, form to the CAA, but no fee. If it's over 5 years, then still a LST and SRG 1119, but as the CAA have to make the entry in your licence, you must also send a SRG 1187 payment form.
Post September 17th, then it seems it changes as described above by Billiebob.