Strictly speaking, these sorts of problems should only be investigated by a Corgi reg. engineer since they involve gas safety devices. Unless you can demonstrate that you are competent (in which case you probably wouldn't be asking the question) I for one cannot advise you.
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.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local