Sorry i've not been aroud for a couple of days, but i'll try to catch up!
GraemeK - The nutrafin system is basically the same as the DIY method. Alot of people actually buy the kit, then use the sugar yeast method with the bottle and equiptment supplies instead of buying the 'proper' refills. It is a pretty good price, £20 being average in the shops. If I remember rightly, each kit does upto 20US gallons.
Les - The idea of the gelitan in the DIY method is to in theory give a steady release of Co2 into the tank. The way this works is by mixing the sugar into the jelly mix and letting it set, then when u add the yeast and top-up water, it slowly eats into the gelitan/sugar mixture to give a more steady production of Co2. I have tried this method myself but found little difference in the efficency to the non jelly method, but was much more messing around to prepare, so I still use the conventional way.
charlie - Yes the reflectors are pretty cheap, as u mentioned £6 which is sightly cheaper than what I paid for mine! The only proplem with using foil is over time it goes a dark grey color and loses its shineyness, I think its because of the water vapor under the hood.
There is another Co2 system which is by far superior IMO, altho it may prove difficult to get hold of! Its the sochting carbonator, u can see a picture of it
here and some info
here. It goes inside the tank, so no airlines, etc. One carbonator does upto 250 liters! These work by a chemical reaction, rather then by frementation like in the DIY method. Each refill lasts for around 1 month, The carbonator itself is normally around £25 and the refills are around £6 for a pack of 2, but I think they are well worth the money. There are no online stores that sell them (that i know of) so if u are lucky enough to have a lfs that sells them then I would deffinatly get one.
And if any of u are interested, my recipie for the DIY is 2 cups of sugar dissolved in around 2/3 of the bottles capacity, then allow it to cool , then mix 1/4 teaspoon of yeast to some warm water and fill to around 3-4" below the top.