I know about the keep it in the blue trick but I'm not succeeding. I'm sure I managed to kill him ok in the Alpha I had access to but in the Beta he's shot me a dozen times when he first appears in front of me while I'm still getting organised. Seems it's a lot harder. I've watched numerous youtube clips and none show the ring in mine nor do they get shot at in the first pass.
I've noticed the NPC difficulty seems to have increased as well so I don't think you're imagining the difference in difficulty between Early Alpha and Beta release.
Other tips I would give are:
1). If at all possible invest in a decent stick, I first played with a 360 pad and then moved onto using an x52 and the difference is incredible. Remap the controls to your liking but make sure to map the manoeuvring thrusters (up, down, left & right) to something easily accesible as these are invaluable in combat.
2). Watch the gap. So, there is some space between you and the enemy and he's shooting at you, if your energy management and shields are ok then boost directly towards him so you close the gap as quickly as possible, then try and get turned in behind the enemy. If on the other hand your energy management and/or shields are not ok then full power to engines and boost directly away from the enemy to give time to recover before re-engaging.
3). Use manoeuvring thrusters. These really help you stay on the tail of an enemy as well as sometimes avoiding incoming fire, for example if you have and enemy in front of you that is pulling up to try and shake you, you pull back on your stick to follow him, you set the throttle into the 'blue' zone in order to get optimal turning speed, but importantly also use the manoeuvring thrusters, so in this scenario I would usually use the 'up' thruster to give me extra help in sticking on his tail.
4). Experiment with more advanced combat features. Have a go at running in 'silent running' mode so the enemy has a hard time locking on if they have gimbled lasers, or even finding you in the first place. Also experiment with disabling 'Flight Assist' (again I map this to a button on my stick so I can flick it off/on as required), this allows you to do things such as thrust in one direction, and then spin on an axis to face a completly different direction to the thrust of the ship and fire. So you can essentially be travelling forwards and spin over 180 degrees to shot at someone on your tail.
Can someone confirm how do more that just the 10 or so combat missions. Is it all via the multiplayer? If so how long does the ship spin for? I left it for 5 mins without anything happening last night.
Yes, I'm afraid at the moment everything outside of a few combat missions is on the multiplayer side. I also get the spinning ship of doom all the time

plus CTD's, stuck while warping into zones, lag, stutter and all sorts of other issues. I stick with it, keep trying and I find I eventually get in. Sometimes it works great for a number of hours, other times I can't get in at all, but when it works and you get a glimpse of what this game is going to offer when working it is simply brilliant
The only thing I do is when first launching into the game is to give the spinning ship 5 mins and if it hasnt loaded up by then I end task and relaunch the game and try again. (sometimes it won't let you end task on it so I just alt+tab to desktop and then back to the game and it crashes out anyway).