Integration of Magento to Sagepay

We have a website already that is built on Magento (www.lowndeslondon.com). We moved it from one server to another and now the Sagepay gateway is not working - I think that the whole set up for the gateway needs to be written again. Sagepay are very helpful and are saying everything from their side is working. We are looking for someone who can work on it relatively quickly to integrate Sagepay on to the site on the new server. If this proves a successful project then we would like to maintain the link over the long-term with this person to assist with certain tasks and maintenance from time to time