Thank you for your reply and thank you for the welcome!
I thought it a little strange that nobody had replied to this post - maybe people are a little shy around here, I don't know.
I'm running Firefox in Ubuntu. Having read around the forums a little, I have uBlock Origin installed which I understand helps with WebRTC 'leaks'. From what I understand of ipleak.net descriptions, DNS leaks only occur when an ISP DNS appears in the addresses, which is not my case - hence my querying you on the single address. My meta-issue here is failure to access BBC's iPlayer ('BBC iPlayer only works in the UK' error), and I thought I'd check this issue first, if that's okay.
Ublock Origin and NoScript are must-haves with Firefox; Umatrix was too high maintenance, I put HTTPS Everywhere and Privacy Badger just for good luck, and I have been ad admirer of EFF since the 1990s when I was a kid. Unfortunately, Firefox doesn't always have a tight ship. There's a lot of weird stuff in about:config, and it can reveal things you might not have known about. I most commonly see people advising that you disable media.peerconnection in about:config, as well as change your useragentstring to something common and not yours. This keeps getting harder. There are also "rogue CPOWs" to worry about, and weird DOM devices springing up that I have no interest in. It's kind of a pain to have to think about these things, but very educational to learn what they are actually doing. Here's an example of stuff to worry about: http://dpaste.com/369858M
Here's a bunch of user agent strings that you can blend in with: http://dpaste.com/1C17281
I use them for wget as well, which I just learning how to use.