When it comes to old tyres: I had a very frightening experience last spring in Italy with 5 year old Continentals. They nearly lost all grip on a wet downhill street.
Changed to new Vredesteins afterwards and they are excellent in wet and dry conditions.
Thanks for everyone's help and advice. For the sake of a modest price I certainly don't want an experience like you had. Going with Vredestein Sportrac 5 - tyres are clearly a very personal choice (as is everything with Morgans!) but several people on the forum seem happy with Vredestein and as my wife is Dutch....