Thank you as soon as I get some time off work I'll try thatI think you've got a TD5 haven't you? In which case, it's not too hard to take the instrument cluster off - screws either side and underneath - and from that point you should be able to see where the bulbs go. It's a so-called 286 in the smaller instruments and a couple of 509Ts in the speedo. Tweezers are helpful.
Sorry yes I forgot to mention I have a TD5Really? That's a surprise, with no knowledge on the subject, I would have expected the 300 to be cable.
The op never said what he had.