[B'master] We may have agreed that a maximum of 2 'on the go' is acceptable, in which case it's only fair that rab or Darren can post a new toon being as how they are the latest correct guessers.
A clue to No 18 - I've attempted the main [and most recognisable] theme of my 70s TV show - there *is* an introductory bit if anyone needs more ...

No need - it's The Good Life.

[rab] erm ... no. I'm now thinking I haven't done it very well.

OK then... it didn't quite fit!

OK...
plink plingyplink, plink plingyplink
dada daa-daa-daa-daa daa-daa-daa-daaaa
daa-da-daaaaaaa
dada daaa, da-daa, da-daa, da-daa
da daa-da-daaaaaaa
dadada-daa-da-daa da-daa daa-daa
didididi-dee dee-deeeee-deeeee
dididi dee di-dee di-dee da daa-da-daa
da daaaaaa-daaaaa-daaaaaaaaaaaaaaaaa
hahahahahaha!