So I have this circut, and need to find the individual voltage and charge of each capacitor. I've been using Q=CV and tried treating the capacitors as both in series, and as 1 in parallel with 2 and 3. I'm not sure where I'm going wrong! There's a full description of the circut and variables with the image. Thank you!

Well since you haven't posted your working I can't check on that.

But I can tell you that your approach is sound.

1) Assume that C1 charges fully to the 100 volts at switch position A.

2) This places CV = 15 x 100 = 1500 microcoulombs on C1

3) C2 and C3 do indeed form a series combination which I calculate can be replaced by a single 12 microfarad capacitor.

4) When the switch is thrown to position B the fixed charge, calculated above, is then distributed between the two capacitors in parallel (the 15 and 12 microfarads ie 27 microfarads) and the voltage changes to an unknown value, but must be equal to Q/C(parallel) which I make 1500/27 volts.

Well since you haven't posted your working I can't check on that.

But I can tell you that your approach is sound.

1) Assume that C1 charges fully to the 100 volts at switch position A.

2) This places CV = 15 x 100 = 1500 microcoulombs on C1

3) C2 and C3 do indeed form a series combination which I calculate can be replaced by a single 12 microfarad capacitor.

4) When the switch is thrown to position B the fixed charge, calculated above, is then distributed between the two capacitors in parallel (the 15 and 12 microfarads ie 27 microfarads) and the voltage changes to an unknown value, but must be equal to Q/C(parallel) which I make 1500/27 volts.

But when the switch is in position B, aren't all 3 capacitors in series? The battery is not connected so thats a dead end.