The bloody government keep changing the goal posts!
I have a tacho but have never used it as I work in an office and have never needed to but some-one told me I have to have it validated every 6 years and some-one else said now I don't have too!! So confused I only want to go to shows!!
If your lorry is less than 7.5 tonne and older than 2007 and you only use it for privately then you dont need to use the tacho and for the plating as long as its seals are intact i dont think it would need a re calibration, have you filled out or got the form for tachograph exemption??otherwise the test center will and should be able to advise you. hope this helps