A750 is no longer supported by KV, so i'm surprised it's still working.
Are you sure it's not an A780 ?
Anyway back to the point, no you can't have catch up, a newer "sub" type box will work pretty much the same as you have got
but you will get HD channels and more importantly a much more stable picture.
A sub will cost about £60-90 per year for cable.
You will need to put in a bit of code called a "C or N line" into the box so it
knows where to look for the data to clear the $ channels.
Have a read around the "general cable section" there is plenty of info about, then just post again
if you need some more help 👍