Ollie,
Working backwards from your quoted figure of £990 for a full month, with £100 on Host that gives a net monthly of £1090. A quick play with the 'annual salary calculator' lurking on the net would give you a gross annual of £15,800 (assuming no pension contributions) or around £17,000 (with pensions at 8% of salary).
Out of interest do you know what you pension contribution rate is (assuming you have any.....).
How do those figures compare to what you were led to believe prior to joining?
No agenda, just curious to know how far adrift of expectations the salary is, and how far it needs to move to get to the oft quoted 'market rate +10%'