hi chocoholic,
I personally haven't heard of a 'council tax' benefit - maybe there is some sort of benefit you can claim for in terms of being exempt from paying the tax or some reduction of some kind.
The only one I know of is the 'single persons discount' - this applies a 25% reduction in the charge if there is only one person living in the property. Seeing as you are there as well, I'd have doubted he'll be eligible and you'll be up for paying the full amount.
I'd be very surprised if the living arrangement you are in would jeapodise (sp?) any application to an ILR - so long of course you have stuck by the rules and paid up what you are due etc etc.
Some members who know more on the Visa section would know more and indeed if there are certain exemptions/benefits you can claim for etc. Also, speak to your local benefits office to see what they say as well.
Cheers DtM! West London & Slough UK!