No rules about having a dash for MOT, but sharp edges on the interior can be a failiure if the MOT tester woke up on the wrong side of bed, and a really shitty lawman could 'award' you a PG9 rectification order for any sharp bits of metal hanging out, i.e. the stereo support bars and a couple of other unused brackets that I can see in the pics. Best to lop those off and smooth them down with the grinder and repoaint those areas. It will look neater too.
Cable ties holding the instrument cluster are a good look, but proper fixings (i.e. nuts bolts and make up brackets) would be a good idea as if you crash hard enough/flip/roll/bite huge tarmac it will probably bust the ties and rattle round the cockpit, probably smacking you in the head at some point, but TBH, if you crash hard enogh to dislodge it will be the least of your problems!