Looks like another aspect where the rules are WAY different in the US and the UK (or maybe you misunderstand them). Of course, I have no idea what the UK rules are, because though the OP asked for "the legislation", the only ones posted so far are the US rules I posted.
In the US, there is no logging "IFR" time; only Actual or Simulated Instrument time (i.e., that time flying solely by reference to instruments).
Please post the UK rule that says you are relieved of "see and avoid" responsibilities (i.e., can fly "head down" so you can legally meet the Simulated Instrument Time requirements) when flying solo IFR and VMC.