Your fighting a losing battle.
You could have it fully machine polished, then use a high-tech sealant, followed by a VERY good wax with the highest UV protection you can find, and it would still go pink in a matter of months. If you keep doing this, eventually you will burn through the top layer of paint. I went to view a red MkII owned by a semi-pro detailer who had obviously machined it to death and it was going through to the primer in places!!!
If I was you, I would buy some autoglym SRP and a decent wax with UV, and then get used to giving it a quick polish everytime you wash it then top off with the wax - It won't be a "great" finish, but it'll look okay and last a few weeks each time you do it. Then the money you save on machine polishing etc. can be put towards a respray.