Would like to get a very basic daylight B&W CCTV starter kit for home
use, mainly to monitor and record visits from various dodgy door-step
salesmen and conmen.

I've seen simple ones at Argos, etc. Anybody used these?

One problem, my TV only has a single scart socket, which is already
wired up to my DigiBox via my VCR in a sort of daisychain throughput
arrangement, so there's no spare socket to connect and more scart
cables. Also my TV is old and doesn't have any composite AV input
sockets. I suppose the only option is to get a cheap LCD TV/monitor
with either scart/compositeAV input.

Recommendations please?

Your local DIY superstore should sell a 4way scart adaptor which may help 
.(make sure its the one for biderectional use)
You may have to retune your vcr to a different frequency to avoid crosstalk 
.
Or as you say buy a cheep tv (asda tesco etc have then around £60)

HTH
CJ