Hi, finally got out for first proper ride today, been out for about half an hour or so just gently round an industrial estate, getting feel of the bike and then about 15 minutes on the duel carriage way. Came back into a 30mph area and was just about to change down to 2nd as was a bit sluggish and the bike cut out.
Pulled over and nothing worked, battery is just about dead yet its a brand new battery.
Could this be the rectifier or any other suggestions?
Thanks all, Debbie :0)

What does it do when you press the starter?

click?
spin the motor?
something else?

yes rectifier and / or generator.

Bike just cut out. Ignition lights worked fine but nothing on the button. When we got the bike back it would turn over very sluggishly as if battery was dying then it went flat. Stater motor keeps clicking. The battery has just not been charging up as its been ridden and having lights on has obviously just drained it to the point where theres not enough juice left for it to run, so just wondering if its the rectifier

It sounds like you have the infamous charging system issue. I'm writing this up at present, and to be honest I'm ending up with a document like War and Peace.

Get a multimeter and measure the battery before charging to see how discharged it is.
Charge the battery, measure it to make sure it's properly charged and fit to the bike.
Measure across the battery terminals with the bike idling. Lights off should be a good 13V or a bit more (I think it's supposed to be 13.5V, but I'm used to an NC35 which is slightly less as you can't turn the lights off).
Measure at 5K rpm with the lights ON. You should have 13.5-15.5V, preferably 14 or more. If you have less than 14V, the system is inefficient, and less than 13V is very likely to lead to the battery going flat. If you have more than 15.5V, the reg/rec is not regulating the circuit correctly and will be damaging the battery, which can lead to it performing very badly.

If the output is low, or the circuit isn't charging the battery at all, take the seat panels off and check for corroded or damaged wiring at the connector for the reg/rec (left side of subframe next to the CDI). Also, check for the same where the alternator wiring connector passes through the right side fairing bracket by the rider's right knee (white connector, three yellow wires). These can get all nasty, and eventually lead to voltage drops and broken wires. Finally, make sure the earth cable for the battery (I think it bolts to the frame on the left side under the rear of the fuel tank on an NC30), and the earth point on the wiring loom are not damaged or corroded. I'm not quite sure where the wiring loom earth is connected on the NC30, on the NC35 it is a ring connector that is bolted to the frame at the same point as the right side fairing bracket.

After that, there are other things you can measure to try and find issues, but they usually turn out to be fried reg/recs or crap wiring.

Wow! Thank you, looks like i'm going to be busy!!!

Best case scenario is that one of the yellow wires in the reg/rec plug has corroded right through due to the way they face down and get crap and moisture thrown at them. I came to a halt after five miles with a freshly charged battery, and when the bike was recovered, the fault was obvious, as I saw the broken wire hanging out the connector - it was that badly corroded! It'll take a bit of time to fix, however unless your reg/rec has fried itself and also knackered the battery, there won't be too much expense. Mine gave up eventually without causing any damage to the battery, it just seemed to stop giving an output rather than stop regulating it, which was a bonus.

Get a meter out and post the results. There are plenty of people on here very experienced with the issue and will be able to diagnose anything really odd. I'm just relaying what I've picked up from them!