Incase any of you guys are interested, I came up with two answers to the starting problem.
1. I bought a small power pack assembly, about the size of two mobile phones, that comes with a set of jump leads, and has enough power to start a car. it was just £34 and also has a USB port for charging a phone if needed. I will take a picture later, so you can see.
2. When I got the bike back in June, I fitted a new MotoBatt battery, I always fit new batteries to any bike I buy, as it takes the guesswork out of the equation. But when talking to a friend about this, he told me to change the battery again, to a Varta maintenance free type battery, as these have a higher storage voltage, not a lot higher, but over 12.6V. So that is what I did, and even during this cold weather, I have had no further problems so far.