Adding a resistive path between live conductors and earth - safety issues
(This answer refers to UK regulations, as the questioner is in the UK.)

Given 2MOhm resistance as discussed in your question, earth leakage current would be acceptable at 0.1mA.

Another point to consider is that the class-Y/class-X capacitors which are typically used for RFI suppression are put through safety testing, and are required to fail open circuit. The same may not be true of the resistors you choose to use.

According to the 16th edition wiring regulations, there is a limit on earth leakage current for class 1 appliances:


  5.9.3
  
  Maximum permitted leakage currents are listed in Appendix L of the 2nd
  Edition of Guidance Note 1, and vary from 0.25 mA for Glass II
  appliances to 3.5mA for information technology equipment (see {7.8.2})


Appliances with higher leakage must have warning labels and a high integrity earth connection.


  7.8.2
  
  Any piece of equipment having a leakage current exceeding 3.5 mA must
  be fitted with a label adjacent to the primary power connection which
  reads:-
  
  
    HIGH LEAKAGE CURRENT
    earth connection essential
    before connecting the supply
  


5.9.3
7.8.2