Appendix 7 of the APD manual (available online) has suggested mixes, both HeliAir & Trimix.
Need to keep ppO2 no more than 1.3 bar at max depth (often 1.0 - 1.2).
APD suggest:
Depth Timix HeliAir END
50m 21/26 15/29 30m (or try 16/26)
60m 18/36 13/37 30m
70m 16/44 11/45 30m
80m 14/52 10/52 28m
90m 13/59 9/58 26m
100m 11/64 7/67 24m
The HeliAir mixes seem a good choice as you don't need to worry about O2 clean dil cylinders & been CCR the unit will add the O2 for you... then there's the bailout to consider
