That connector in the link is NOT the one that will fit this tacho.....the connector referenced in the link I have literally thousands of. It is an 8 pin dual row AMP 040 series. Give me some time, and I may be able to help you a bit more. The connector looks like it might be from the AMP 070 series (similar but different).Bigbadboab's link is probably the most helpful one you will find.
Take a close look at the link and you'll note that it includes a reference to the connector plug you may need, Amp 174044-2. I can' t begin to tell you who in the U.K. can supply that part but check with companies that sell electronic components directly to the public. Failing that, I suspect that the back of the gauge has male "pins" that you could connect to using small female crimp contacts on discrete wires. Can you post a close up picture of the back of your gauge? I know you've got a distant shot of it already but a closeup would help.
Carebont IS Smiths. Smiths dissolved (sort of) . There is still some form of aerospace division of Smiths and an electrical connector division was created and operates as part of Interconectron/Hypertac. If I remember correctly, a group of former Smiths employees got together and bought the tooling and technology of what was left of Smiths Instruments and re-incorporated as an independent company, Caerbont.
Look carefully at the connector - does it appear to be a single row of 5 pins, or are there empty spaces where additional pins might be fitted? Perhaps another pic face on so I can see the pins/housing might help.