I hve just done a gas meter reading and it looks like I have used 750 units in 3 months. A colleagues has used about 170 units in the same time.
I have a detached house and he has a semi we both have 11 rads and have the heating on at similar times, there are 5 in his house and only 2 in my house so we use less hot water.

I have gone from being in credit by £1000 to a debit of £300

This seems a big difference between us?