All - thanks for the help.
Sorry for the delay in getting back, I have been away at a concert! I even used the car to get there - a bit of a risk.. buuut - whilst there, I solved the problem.
A dodgy earth wire in the trunk from the CD changer to the earth point had fried - looks like I used the wrong guage wire... and hence was discharging the battery by a "slow cooking" method... lucky it didn't cause a fire...
It has got me thinking about other potential (pre-me!) DIY bodges that I may need to check out upon your advice... power antennas, fuses (locating power problems with a meter.. I have one.. yes).. I think I will do the "full monty" and ensure we all safe in there.
Thanks again 92400E, tkamiya, dlswnfrd (brother of the Benz??) - cheers & if you have any other W124 wagon general advice - let's hear it!
1984 W123 230E Saloon/Sedan! (82k miles - Ice Blue as new)
1985 W123 230TE (96K miles - stinkingly nice!)
1995 W124 E320 Wagon (130k miles)
Sportline Suspension W124, W123 TE restoration, A/C, cruise & powered seats retrofit!
>Based in the UK!