You don't necessarily need another test.
When this whole LPE scheme came into being, the UK CAA recognized from very early on that most UK license holders would be native English speakers, and having them do a separate test would be somewhat ridiculous. So they came up with a grandfathering scheme.
If you do a flight exam (LPC or whatever) with a UK JAR-FCL examiner, who is him/herself an LPE six, and this examiner finds you are a native speaker, then this examiner can issue you with an LPE six as well.
But here's the catch. If you are not a six, then the examiner cannot help you and you need to go to a proper language examination institute to verify whether you're a five, four or (god forbid) even less.
As you just recently did your FRTOL and LPC, I'm surprised that none of your examiners used their privileges to give you an LPE six straight away. It might just be an omission on their part, since most of the UK pilots were grandfathered this way over a year ago.
The LPE six is recorded on the SRG\1199 form and I believe there's another form as well on which the LPE six can be recorded, IF the LPE six is the result of this grandfathering scheme. If you do a proper LPE test at a language institute they will issue you with a formal certificate which will list your LPE level, and that's what you need to send to the CAA. (At least that's the way it worked for me. As I live in NL, there were no convenient UK examiners nearby who could grandfather me into a six. So I had to do a formal LPE test at a language institute.)
Last edited by BackPacker; 5th Oct 2012 at 18:59.