Can anyone tell me what chemicals i need to make an aromatherapy diffuser liquid apart from essential oils? i live in the UK so need to be able to buy it here.
There is a bit here which tells you one method, though where you get the ingredient to dilute the essential oil is anyone's guess !
Because you don't put diffuser oil on the skin, the manufacturers are not obliged to tell the public what the ingredients of the base are. Best guess is alcohol or the Dipropylene glycol mentioned in the link. If you are thinking in terms of an oil burner, alcohol might not be a good choice.
Try your local chemist. Even if they don't have it in stock, they may be able to order it for you.
As you want to make this stuff for a reed diffuser, you might be able to get away with alcohol. Try mixing some essential oil with vodka, if you have any to hand, and see how that works. If you use a small quantity of both it shouldn't be a very expensive experiment. And if it doesn't work, you'll still have plenty of vodka left to console yourself with :-)