I wouldn't be sure it would work anyway.
The older Pace boxes and the black remotes use the IRDA protocol to send IR signals and having had a quick look at the Bluedelta site, I can't see anywhere that it supports it. That's probably why it doesn't work now with your existing remote. Have a look here for a bit more info and a potential solution -
http://www.redremote.co.uk/
If your Pace box is a 4001 or 4010 then it uses (more standard) RC5 protocol, the blue remotes will work and you're laughing.
If you do need to get another remote, eBay is your best bet - usually you can pick one up for less than £5 inc postage, just search NTL or Telewest remote.