Headlight Headache!!!!!

Hi, I own a 03 Range Rover Vogue and have been having a few problems with the front passenger side Headlight. It keeps coming up as a fault on the computer which changes depending on it's bloody mood!..sometimes the main beam works other's it doesn't, then sometimes the side light does/doesn't work. I took her into the garage who have ended up putting in a new bulb and a new charger unit to the tune of £300.00. However this has not solved the problem and now they reckon I need a whole new unit.The garage contacted somebody who quoted a £1000.00 the garage guy said no chance at that sort of price but what option do I have???!!! The garage guy is a family friend and has never been unreasonable on price and to be fair he was the one who said no to the quote any advice on what's wrong or where to get cheaper parts from?