Noisy pump?

Just had a 'senior moment' and posted this as an answer...
My machine is now noisy. It souds to me like the pum is making the noise. When the heating comes on or the hot tap is used, there is a sound, which to me, sounds like worn bearings. Plus, when the heating goes off, before the noise would stop immediately. Now there is a sound like a motor slowing down gradually over three or four seconds. As if the bearings were before silent, and now you can hear them. Would that be a sensible diagnosis?
If it is, is changing the pump 'simply' a case of draining the system, changing the pump, then refilling?
I have found a supplier of Potterton parts and they quote a new pump for £56 plus the dreaded. It won't arrive before christmas if i order one now. How long would you think the pump will run as it is? I first noticed the noise last friday.
Thanks