Small flat, Scottish Power, gas and electricity currently £65/month averaged over the year. Electricity similar to mine if you take off the fish tank. So £100/month over the last 3 months seems reasonable. Doubt it will be £100/month for the next 3 months. Don't trust the £94 DD SP has imposed on you. Likely to be high over the year. They're probably at it.
Couple of things you need to add to your list
(1) Water heating whether by gas or electricity
(2) The electricity consumed by the boiler
Are the readings for 20/11/08 and 18/02/09 both actual reads or are one or other estimates? Can't do a proper comparison without doing that.
Also its useful to convert the gas usage to KWHr. Not easy but the bill explains how.