Mk1 Octavia eating Alternators

Excuse my lack of correct terminology, but not into cars, but nonetheless would appreciate any info/ thoughts on what would be a sensible course of action.     I have a 2004 Mk1 Octavia - I bought it 2010 and have put 70K of its total 121K miles on it.   It has been serviced regularly, and when informed by garage that whatever needed doing, it was done.

In January this year alternator failed, took it to local garage (my norm would be 30miles away) and they fitted new alternator.  2 months later major failure on motorway when all power again lost and when they replaced alternator and battery they hadn't bothered to attach connection to battery and it had been bouncing around and shorting.     New battery got me to my trusted garaged, more money back on road again.   Normal service and MOT in September and then today when battery failed - recovery got me to a local garage and I've been informed £400 ish to replace alternator again and they have advised new battery.

Oh and also have water in rear passenger footwell behind driver side - can see where it is coming in - and seems to be contain in the rear as I park facing down a slope.

My questions are what is a the worth of my car?  Is it worth spending yet another £400 - bringing this years total to over £1000?  Should I just scrap it?  If it is worth spending the money, am I getting value - they say they are going to use a bosch alternator.

Many thanks for reading.

J