convertible battery replacement

Hi Peps

Up until Saturday my sportline had been parked up for 5days(with the Clifford alarm on). As the weather was nice I dropped the hood and went to start it and……….. you guessed it no response, dead battery. I jump started it and it started straight away. Im guessing it needs a new battery. Because  I drove it for an hour, parked it and it started again after 3 hours.
This  had been the first time I left it without starting for 5 days.

my question is what battery shall I go for?
im thinking bosch 063?
However these rang from £40 to £90 pounds depending on the crank power and amp

What amp is best or shall I get the original from VW?

please note I barely drive the car(once a week, if the weather is good)