Wilo pumps aren't as tolerant to filth in the system as Grundfos pumps are and will likely fail if the water isn't kept clean.
For the effort of putting in a new pump, and the relatively small cost, I'd personally replace with a grundfos and know that I had a good pump installed.
Have a look on eBay for one if you want to save a few quid. I presume you have valves either side of the pump!?
Thanks for the advice and yes, there are valves either side.