Landlord retrospectively charging for Gas Service charge...

PositiveTension

I just wanted to see if anyone could give me advice on this, i'm not sure if this is fair, or what rights i have. In bullet form:

- Moved in to my current apartment in June 2008 on a 6 month contract, rent was inclusive of any building service charge

- Received a letter in October 2008 saying that they had only just been advised by the building management company that there would be a gas service charge for space heating via a boiler in the basement and they'd inform me of the charges.

- Renewed my tenency in November for a further 6 months.

- Got a letter in Feb 2009 saying they had received the charges from the management company, asking me to pay the charges from June 08 through to Feb 2009 and that i was to add £25 month from now on to pay for it. This came along with the bill from the management company, citing the 'Apportioned Gas Service Charge'.

So basically i'm wondering if this counts as a service charge, or as just another utility bill as my landlord is saying. I obviously don't mind paying for the period from the notice i received as i effectively accepted it by signing a new contract - its the period before this that i'm unsure about. The landlord has now said it's based on consumption from a seperate meter reading for my flat, but the copy of the bill was charges in advance of the period it was for, so i don't see how that can be the case.

Apologies for the long post!

Any feedback would be welcome

Thanks