Don't even get a DNS resolution on ping or tracert, so certainly does feel like some type of IP block.
What specifically happens when you access the website for the domain those music streams are being served from. Go to http://www.smgradio.com
and watch exactly what happens then post back.
For me here (in Australia, using Firefox 220.127.116.11 browser on Windows), that URL directs to http://network.virginradio.co.uk/
and down at the bottom of that page the last line of text says "You're connecting through (my IP address), in AUSTRALIA, to smgr. This is a peered connection." (then a link to click through to a page about the peering agreements they have in place around the world).
I'd be interested to see if you get the same redirection from www.smgradio.com
(if it redirects then _it_ is getting resolved), and also what if any interesting information is shown on that last line of the redirected page (assuming it successfully takes you there at all that is).
BTW if the problem you're hitting is "simply" a DNS resolution one (rather than any deliberate blocking of the IP address range you are in), I resolve www.smgradio.com
here as 18.104.22.168, so you could try replacing that in either the stream URL I posted earlier or your browser and see if that makes any difference.