SFIM
The important part, the thing that is going to set things in motion, is to send the " RPPL-F-100E" to the IAA.
By all means the forms that you need to be sent to the UK CAA are also important. However the UK CAA will not do anything until they receive a formal request from the IAA to provide information about the licence, and medical data, of the applicant that is applying to change SOLI.
de facto
About your question regarding the "licence copy must be certified", if your licence is "as issued by the CAA", in other words, if since it was issued by the CAA there were no handwritten entries made on the licence by a TRE, in case of an LPC, then the copy of the licence needs NOT to be certified. Search the UK CAA website for "How to get copies of your documents certified". At the end of the page it mentions what I wrote on this paragraph. If you however did any LPC's since your licence was issued, and this were endorsed on your licence by the TRE, then I'm afraid that you will have to certify the copy of your licence. There is an explanation on the CAA website on how to get this done.