Thanks everyone for your most valued input. My own bank, messrs. Lloyds TSB have never mentioned the trusteer Rapport software as a requirement to improve the security of banking transactions. They appear happy to rely on their own security systems with which I have never had a problem although I do my best to ensure that no nasties invade my machines.
In the case of MBNA the only access I have or need is the ability to read my statement. Apart from seeing part (but not all) my card number no hacker would be able to obtain my PIN or any other numbers needed to authorise a payment thus I feel fairly safe in not installing this software of dubious quality.
P.P.