I'm in the south-east of England..
I know what you're feeling.. I'm glad my two MBs are highly optioned, both have 4 electric windows & roof, rear headrests, original 15 hole alloys, auto, 190 has MBtex seats, 300 has electric leather & climate control.
There are plenty of MB breakers, I would look into finding some MBtex (very, very similar to leather, tougher wearing, cheaper) or leather seats from one - this will probably be cheaper than you'd think, and will improve the car *massively*, making it feel much more expensive & luxury.
Also, many companies will re-cover the seats with leather, i would definitely look into this if you may have to re-cover the cloth anyway.
Similarly, I would go for some original MB alloys (15-hole), but I searched everywhere for a good condition full set for under £300, and in the end bought poor condition ones and had them repainted & re-lacquered.
I keep seeing neglected ultra-basic MBs with huge, out of place shiny alloy wheels - why?
This would ruin about the only remaining thing such an MB has going for it - it's ride quality.
Why don't the people spend the money on the parts of the car that need it first? Glad to see your fixing up the damage & the bits that *need* improving!
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black