On the UK CAA IRT one is supposed to add 50ft anyway to the altimeter reading for the DH (I am told) so 200ft is never actually achievable.
Not quite - see para 6.1 of AD1-1 in the UK AIP. In short, details of PEC for
your aircraft should be in the AFM/POH. In the absence of such data then 50' has been found to be suitable for a wide range of light aircraft. A good example of when not to add 50' is the humble Grumman AA5, where the POH specifies a PEC of 15'. Don't be put off from fighting your corner when you're right
