Much thanks all for the tips - I managed to get in contact with the ENT last Friday and the result was Lichen Planus. Such a relief.

They have run a bunch of other blood tests and I am waiting on the results of those to see where to from here. I definitely still want to keep an eye on it but it's so hard to know exactly what might be causing it. Will have to see what can be done next.

Thanks for your support,
D