Hi Michael,
We have just switched from Brit Gas to Powergen on 1st Aug so cannot tell you what our new supplier is like yet.
Cannot get dual fuel where we live (in a Park Home) because we buy our electricity off the site owner. But probably at a better price because he gets one bill for the whole site at a bulk rate and we each pay for what we have used on our meter. None of this where the first X units are at so much and the rest at another rate.
As you will be a new customer of any gas supplier do you have a choice of who you can use as a supplier?
If so choose any one EXCEPT BG.
In twelve months time use the comparison company Energy Helpline BUT link to it from here:
http://www.moneysavingexpert.com/utilities/you-switch-gas-electricityand, if the offer is still on, they will pay you £15 of the switching fee that they get for changing you over.
It will take about a year to get some average usage figures for you gas demands, then you can get single or even dual fuel pricing comparisons.
Hope that helps
dave