I am in transition from using a managed domain / web
service for a
couple of sites.
I'll be cancelling the old web space account but not sure how to
proceed with the domain / dns hosting aspect.
Firstly, get your domains transferred to a decent registrar if they
aren't already. I won't suggest a registrar as there are so many and
everyone has different opinions on which is best.
With regards to DNS..
TL;DR: Unless you have specific needs (in which case you probably
wouldn't be asking here), I'd strongly suggest that you just use the DNS
service of your domain registrar (at least to begin with).
Long Version:
There's usually quite a lot to consider when it comes to running your
own DNS server.
You'll need to have at least two servers, an authoritative server (that
you would control) and a secondary which will kick in should the primary
be unavailable and continue to service requests, but bearing in mind if
your VPS is down then both your DNS and web serving will be down anyway.
BIND or PowerDNS are popular examples of DNS servers. Bitfolk (Andy) is
kind enough to provide a free secondary DNS service should you need it:
http://bitfolk.com/customer_information.html#toc_2_DNS_secondaries
You'll also need to set up nameserver DNS entries pointing to your DNS
server(s) e.g.
ns1.yourdomain.com, if you want to use your own domain as
a nameserver for itself (e.g.
ns1.yourdomain.com as an NS entry for
yourdomain.com) then you'd need to get your registrar to set up glue
records to allow the circular dependency to work properly.
If you'd like a challenge or if you're going to be setting up a web
hosting service where dynamic DNS configuration would make your life
easier, then by all means give it a go. If not, then I'd suggest that
you save yourself a headache.
Cheers,
Luke