Realised what I did. I took the sample straight out of the recirculating arm without letting it run for a bit meaning I got a load of wort post mash and pre-sparge. I realised this when I did the same thing post boil and the sample was only 30c. Another one to go in the experience book. The correct OG was 1.042 (post boil) so near enough spot on.
Was racking my brains for ages as temps and volumes were all ok.