dmorison - 2:22 pm on Jul 16, 2013 (gmt 0)
Hello Scott, and welcome to WebmasterWorld!
1) Should I leave NS with the registrar and point an A record to my VPS IP?
Yes, I think this is what most people do unless there is a good reason not to, and it's one less thing to worry about managing on your VPS!
The big registrars that also offer DNS for your domains are very experienced at running DNS and they likely have considerable redundancy etc. in place - there's simply no need to have your VPS deal with DNS when your registrar is offering it as part of their service.
2) If so, what about the other DNS records? Do I change those with the domain registrar (Fasthosts) or on the VPS via Plesk?
It all needs to be done in the same place, so if your domain record points to fasthosts as the authority DNS you need to manage all record types there.
And further, if your VPS control panel allows it you can / should disable DNS service as there's no need to have the ports open if they're not required.