Thanks for the replies. I live in a relativley flat part of the world (Formby, Merseyside) and find a 50 / 39 combo that I have on my winter bike really useful. I use a 12- 23 cassette and find the 39 inner for the hills around Parbold and Ashurst Beacon fine (Bank Top is a bit of a beast though on the 39 - 23). Often the wind is my main enemy and with the 50 I find I can bash in to it with a better chain line than on the 53. Yes I probably should use the 39 a bit more but my ego likes to use the outer ring.
Doing a bit more research I think the SRAM powerglide.chainrings are made by Truvativi. Struggling to find a source though. I expect the strongling rings would be just as good though.
hills around Parbold and Ashurst Beacon fine (Bank Top is a bit of a beast though on the 39 - 23).