Had a good look at Conrad and found the same items for a lower price from the UK http://www.rapidonline.com
Going for 10 and 35 teeth gears with two stages of 3.5:1 for a final drive of 12.25...that will fit in the space I got, the 48T gears will be too large and will require quite a lot of work to fit in.
I estimate the weight of the motor and gearbox to be around 340 gr each, that's a weight saving of 110 gr over my current setup...I desperately need to shed off weight!