According to Thames Water's pricing information, customers for metered waste water pay 64.73p per cubic metre of disposal during 2012/13. That of course is calculated having factored-in the percentage as we mentioned above - typically 90% of the amount supplied.
We don't know where you live (nor need to know), but £2 per cubic metre disposal charge does indeed sound horrendous. There are a number of small water companies in the 'rural ring' around the north and west of London and I suspect you are with one of those.
You can interrogate Thames Water's postcode system here to see if they can deal with you - though I suspect this is going to involve a phone call if you are that close to the boundary between regions.
http://www.thameswate...k/moving-home/605.htm
Whilst I said earlier that there may be some overlap between suppliers on the boundaries of 'competing' companies (and I use that term very loosely), I think this may only apply to water supply, not disposal. The implication of having dual sewers on the edges doesn't really seem practical.
It would be interesting to know who this expensive company is.