Help with some B5 bits and pieces

[runepig]

Have had a search for a bunch of things and found some good answers so far, but could do with a bit of help with the following if anyone has some advice (or can point me to any threads I've missed). Have a B5 TDi 90 S saloon from 97, mostly dry! Found a puddle in the left of the boot but think I've found the gap in the light cover that needs sealed. Front drains are fine far as I know.

Central Locking (non-remote)
This mostly works but the from passenger door doesn't lock with the others (either from key or button beside driver's window controls). You can lock it by pushing the button down and the central locking will unlock it. Also, the boot key triggers the central locking (lock and unlock), but the boot itself doesn't seem to lock.

Vents
All the air vents seem to have at least one up/down plastic strip that doesn't work (some of them are all boned!). Are these fixable or should I pick up some replacements, have to see a guy breaking some Passats for a headlight anyway.

Radio
Reception sucks! Have ordered a cheap eBay aerial but suspect it's the aerial base as the seal as perished a bit - another breaking job or are the eBay bases ok?

Biodiesel
I know these engines are rated for B100, and have run other cars from same era on bio, but am having a debate with my mechanic (also father-in-law) about it's merits. No bother so far, but I've read some advice on other sites regarding changing the fuel filter (has a new one) after a tank or two/1000 miles/6000 miles etc. Any experiences from the Passat ninjas on this?

Thanks for any help.