I'm looking for a warmed up A15 for my wife to drive as a daily and I have access to a newly modded engine bored 78mm 12:1 compression with dual webers etc Seems to me this compression probably better suits a race engine/may need high very high octane fuel/ be too lumpy for her. What do you reckon?

As much as Dual Weber set-ups are reliable, An engine with a single carb may prove to be a better option long tern, especially if driven daily. Reliability is where its at with daily drivers IMO 12:1 comp ratio may also be of concern based on your availability to higher octane fuels. At face value 98 premium fuel would be the go, anything less may lead to engine issues.