Joe wrote:
Not quite... You have to specify the start date for each
travelcard
and can only buy them one month in advance. You could pay the
deposit
and for the first 7 day travelcard the first time you come and then
buy
another 7 day on it the second time

Couldn't the OP do prepay and then let the capping take over, or
wouldNt that work?

He could but:
a) It would be more expensive (caps at daily rates - not weekly)
b) He wouldn't be able to use it on most national rail services because
prepay with a cap still counts as prepay