The common one you missed out is WAT1, which is Water Heaters, like the Chaff Britonys, Main Medways, and more modern things like Rinnais.
If you want to do Landlords Gas Safety Checks you'll need it.
Numbers 5 and 6 would be Warm air, DAH1, and Meters. You may have estates with a few warm air heaters left near you, but Meters isn't much use. Only for Landlords Meters really, you still can't touch the Gas Carriers' meters.
I've got Driers, and have never used it!
LPG - deoends on what's near you. TBH it can be a bit confusing to start with the two at once. Maybe add it if you need it, later.
The oddity at the moment is Flue Gas Analysis. It's going to get combined with CCN1 or summat at some point, we think, but for the moment you have to do it. It's very short though so is combined in some way at most centres.
Ask your probable ACS centre about exactly what they want to see from you. They'll vary, partly in their interpretations, and partly as a result of working with different boards. (eg CITB, etc)
I'm a part time ACS assessor, but the blokes are through the admission stuff by the time I see them so I don't know the details. I can tell you all the centres are dead quiet at the moment so you should be able to squeeze a good deal somewhere! Don't come to us, you even have to pay for your coffee!