The first couple of months will be BASIC. (£500-£600 take home) You start to earn your sector pay and commission in arrears, so it takes a couple of months to kick in.
Up until your 6 months probabtionary period, expect to clear £900-£1100 per month. Dependant on how many sectors you do, and how good your selling skills are. LGW is one of the highest bases for commission. After your 6 months, you'll certainly notice your increase in wages, and we are one of the better paid european airlines. They do work us hard for it though. Staff travel straight away (Not 3 months as I had to wait) for £30ish Return, and although usually not a problem, staff travel isnt always available on the dates you want.