Is there any benefit to having my own tag?
Also, what's involved when you own a tag? If I own my own tag but am not hosting the site myself do I need to find a DNS service? What else do I need to do to allow a US hosting company to host my site?
Or should I just find a UK registrar who'll just do the registration and DNS and let me host the site in the US? How do I find one of those (I'm assuming that anyone who does the registration would also want the hosting business... but I really like Brett's hosts and want to stay with them)?
Is there any benefit to having my own tag?
If you intend to register 10 or more domains per year then having your own tag can be very useful. Effectively it gives you complete control over the domains.
You will need two DNS servers to act as your primary and secondary (I think that any DNS servers are okay but you will need to check this out.)
You can host anywhere you like, there are no restrictions.
Nominet membership will cost £400 or thereabouts initial joining fee and £125 per year, but you get domain registrations at £5 for two years.
Many of the UK registration companies are not just after the hosting, though they try to make it seem like its a good deal to host with them as there is more profit in the hosting - and a lot of the cheapest registration places charge the most for their add on services (they have to recoup their costs after all)