I have today received an email from Lochiel in response to my letter to him regarding the official/unofficial status of the Cameron of Erracht Tartan. The response is in full and the bit about a 6 year old was when I told him of my first visit to Culloden. The response is as follows -


Dear Simon,
Thank you for your letter of 28th February and apologies for not replying sooner. As your mother was a Taylor, I am delighted to welcome you as a member of the clan and hope that it brings you much pleasure.
Culloden has much changed since you were there as a six year old but still strikes me as an idiotic place for the Highland clans to battle the Hanoverian army ! As I think you know, Clan members attend a service there each year on the Saturday nearest April 16th (the date of the battle) and we have a lunch and talk afterwards,
With regard to the Erracht tartan, it is perfectly acceptable for clansmen to wear it. The Queen's Own Cameron Highlanders are now, after various amalgamations, subsumed into the Royal Regiment of Scotland and the Erracht tartan is not used which is sad but, I suppose, inevitable.
With kind regards
Lochiel


So there we have it Cameron of Erracht is perfectly acceptable for Cameron's or their septs to wear, although it still remains in the eyes of the STA and the SRoT officially unofficial.

Its good enough for me that the Lochiel says its fine.