Most chemists stock it and its widely available from t'internet e.g. Amazon.

You can buy Citronella oil and products from most supermarkets, health food ships, chemists and camping stores. They also do it in candle form which would be good if you were camping. I look to our northern brethren for guidance here but I thought midges were only a problem in Scotland May / June?

Careful putting citronella directly on your skin. Some people react badly to contact with it and the good stuff is very concentrated. Try a spot before you go.

spaceprobe wrote: I thought midges were only a problem in Scotland May / June?

Nope, they'll happily devour tourists from May right through till the end of October.
Don't camp near water, stay indoors till well after dawn and if the wind drops around dusk, watch out...
The Avon stuff needs to be continuously re-applied and to work you have to be absolutely coated in it.
A few carefully applied drops of citronella will keep them at bay far more effectively and for longer.
I've done overnight loch fishing sessions using it and never been touched, on the one occasion I forgot my citronella I came home looking like the elephant man.
I put a couple of drops in the palm of one hand, rub my hands together then rub it on, taking care near the eyes.
Its nasty stuff as Bluebottle rightly points out, but its a whole lot better than being midge food.

You can get it from any decent chemist or from amazon

And there are some tiny feckers so any protective mesh needs to be really fine/well fitting.

I remember the air being clouded with mayflies one year near Doenoch, they don't bite but bigger and you had to breath through your teeth otherwise they stuck in your throat and up your nose