No grayling in these parts sadly, although if there were we'd certainly have some of the best on offer in the country.
Closest is the Isla / Dean and other waters in the Tay system, Tay itself, Tummel, Almond and Earn (Kinkell Bridge area a favourite for grayling).
Upper Garry is reputed to hold grayling but unconfirmed and access is very restricted anyway.
Further south there's the Forth and Teith (no idea on access), Esk and Water of Leith around Edinburgh, Clyde (amongst the most reliable and best access grayling fishing in Scotland). Tweed system offers some excellent grayling fishing as well and some big fish are caught each year.
Couple of other waters in the South West but i've not fished these ones as yet and not entirely sure about access / fishing.
Hope this helps