This is probably going to sound incredibly ignorant, but having purchased a DVD player, and having attempted to install it on three different TV sets (all of which are relatively up-to-date), there seems to be absolutely nowhere to insert one end of the AV phono lead - the so-called "video socket" on the TV, as quoted by the manual, simply doesn't exist, either on the TV itself, or the connected digibox - so is there anything one can do?

You say the so called video socket, does your tv only have two sockets then if so one is sound and the other is video, you have to match the colour of the socket to the colour of the heads of the lead - Yellow = VIdeo and Red & White = Sound.
if it don't have any phono (Not all tvs have phonos some just come with a scart), you can buy an adaptor to convert phono to scart.

Oh, I see, yes, there were only two sockets, one red and one white - by unplugging the white lead, and inserting the yellow lead into one of the sockets, it works - thanks very much indeed!

Why not use the scart connections?