Also, some input of Lipo selection would be much appreciated - I can easily get Flightpower or Thunder Power cells. I already have a few packs of TP 3850 5S and FP 3700 5S which I will use for practise, what should I use capacity wise for longer flight times and for competion use bearing in mind weight is an issue.
The TP prolites (around 5000maH) work well for competition use; they are just slightly lighter than the FP evolite F3A 5350 maH packs, which are just a little more powerful.
Both will cope easily with a typical PO9 or F09 schedule, staying well within the 80% capacity suggested for long battery life.
And, whether or not you think it's the right way to go on, the fact remains that here in the UK nobody's going to object if you're a bit over 5Kg at a comp., unless you're trying for a team place.