Whilst I have never been to the trails behind the Nat West in Swindon I have been to rotovagas many times.
The good thing about the uplift is that is serves both the national DH track and lots of other trails that range in length and grade. Ride as much as you can, weather has been mint for this time of the year and it is riding really well. It is a quality bike park, with riding for everyone (unusual for NZ).
It is a real biking town but I would definatly be careful leaving your bike unattended.
Are you in NZ for a holiday, if so I would recommened getting about a bit and not staying in Rotorua the whole time. Oh and the place smells of eggy fart because of all the termal activity.
PS If you see a pair of Oakley Crosslink glasses there let me know, I left them there after a night ride the other day.