There might be more plang-chongs in the intro.

[Bigsmith] Correct! Number 19 is, indeed, Rentaghost.

[rab] It's not the opening from Handel's Messiah is it?

Update:
1. Bob the dog - ISIHAC Theme 2. Chalky - Coronation Street 3. HB - Some Mothers Do 'Ave 'Em 4. Raak - Thunderbirds 5. Kim - The Archers' Theme 6. rab - Roobard and Custard 7. Bob the dog - Pomp and Curcumstance, Edward Elgar 8. Lib - Blind Date 9. ZK - Dangermouse 10. penelope - Blue Peter 11. Watty - Porridge 12. Kim - Tom & Jerry [Fred Quimby version] 13. Herr Bratsche - Monty Python 14. Raak - Star Trek 15. Bob the dog - Dr Who 16. rab - Have I Got News For You 17. Darren - Bergerac 18. Chalky - The Sweeney 19. Darren - Rentaghost 20. rab's plang-chonger - ???

[Darren] Nope. A hint?