Hi Bif. 110s certainly used RR engines but had a 6 cylinder version with mechanical gears (SCG, like most blue square DMUs), whereas the 127s had a hydraulic transmission and 8 cylinders. I'm fairly sure the RR Cravens units had the 8 cyl engines and some (but not all) had hydraulic transmissions but I never ever encountered those in real life so I cannot say what they sounded like.
The 110s and similarly engined 111s seemed to me to have a rather flat and uninteresting engine and exhaust note (I rode them on quite a few occasions between Leeds and York, and sometimes further afield too, to Manchester).
Don't get me wrong: I'm not criticising your choice at at all, I was merely wondering how much demand there will be for the 127 sounds ... and I would still love to hear them in all their glory. Being so far away I cannot just go down the road to even a preserved railway to see and hear these things nowadays. I think my last trip on a traditional DMU would have been in 1986. On subsequent visits to the UK I still rode many trains but the Sprinter families had taken over by then. The sounds provided by you and the likes of Howes do bring back pleasant memories of some of the earlier trips.
As an aside to my SR and LT modelling, I have a varied collection of DMUs, including classes 101, 104 (from Hornby 110), 105, 107 (one DMS only, done as an experiment), 108, 110, 114 (brass kit), 117 (modified Lima), 120 (Craftsman) and 121 (converted from Lima well before they offered one RTR), with unbuilt conversions still to do for 119 and 129 units. I only have sound in the Bachmann 108 at the moment and I wouldn't even consider it for the older Hornby and Lima based units because the running qualities are rather inferior to the more modern models.