Hi david
I am also with Manweb ScottishPower and pay by dd online, with their PriceFall tariff.
I have contacted them in the past couple of days as prices now seem to be on the up, it was in the paper that Npowers new sign online tariff (9) gas price is 17% higher than sign online 8 and the electricity is nearly as high. They reckon this time next month all suppliers would have begun or done a price increase.
PriceFall guarantees no rises until November 2008, or they do another tariff which is Online Energy 4 which has really good rates but dont think they are guaranteed.
As for DD. Well you seem to get penalised where ever you are now adays if you dont pay by DD. All suppliers offer cheaper tariffs for DD than paying quarterly. But I know Scottishpower actually increased its prompt payer discount to £50 for dual fuel in june this year (as my grandparents pay that way) but didnt lower their prices, it did for DD.
I know with DD with ScottishPower they are now only contacting and increasing your monthly dd if your payments are not on track. Also the beauty is, as you know, with an online account, you can keep your eye on it yourself, even put in monthly readings if you want, and this will tell you on a month by month basis exactly what you are using.
The best bit is, if you decide to change your package, to either PriceFall or Online energy 4 you can do this simply via your internet account, via the change my service option, and you can do that now. Again Pricefall guarantees you lower rates than your paying now(as you will be moving from quarterly to dd) and those new rates are guaranteed for the next 11 months. If you decide to change supplier, moving to qtrly cash at your new supplier, you might find when your transfer completes. after 4-6 weeks your rates have gone up again........