Thanks for all the responses which are really helpful. I also appreciate the latter responses, taking a pragmatic approach to the situation but for clarity, the reason I am asking the question is that I am starting out on the IR(R).
Whilst I have been able to make a reasonable assessment for VFR flying in winter previously, the added potential of flying into/through cloud under IFR conditions has made me consider more closely the potential for icing (especially given I am flying C152/PA28 aircraft which are not equipped for such conditions).
I am now much better informed than I was and appreciate that this is a potentially more complex area than I need to understand as a PPL - thanks for the responses.
Jon