on boss' advice, i have restored the subdomain and parked my own;
i was aware of the 48-hours dns propagation time, which is why i was curious about the result of `ping bclodge.co.uk'; it was reaching the x10hosting name server, which suggests that i have set things up well; but then the name server is keeping hold of the request, rather than passing it on to the web server (or whatever is supposed to happen next);
as for the 123-reg name servers, they never caused a problem with my previous host; they pointed at the host's name servers and everything was sweet;
thanks for your responses so far; if you have any other ideas, please pass them on
Edit:
having been using the name server ip addresses given at
http://support.x10hosting.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=2 until now, i have changed to using the name server dns names given on the same page; perhaps this will help, since the name server dns names no longer correspond to the same ip addresses