its not pump as rads would not get warmsounds like it is overheating, you need to make sure the pump is wired back to the boiler for pump overrun and your bypass valve if fitted is open. also needs a permanent live to boiler not just switched live.
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local