ELP
Hey Martyn
Nice to meet you over the forum, remember me???
If you have UK PPL then it should have on it (ENGLISH PROFICIENT) and you can show this to DCA and it should automatically entitle you for level 6 on your DCA license
If you do not have a UK PPL then you either need to get a letter from CAA UK to say that you are a native english speaker /or/ sit for the test, i recommend the latter option because getting the letter from CAA in London is a lengthy process and costly one too
My regards to your kids