Beckenham: Fix a kitchen cabinet/boiler housing unit securely to a wall to ensure door closes properly (ended)

Fix a kitchen cabinet/boiler housing unit securely to a wall to ensure door closes properly

See the pictures. My kitchen was fitted about a year ago (just before I moved in) by the previous owner. A new boiler has been installed, and around that is a pretty standard kitchen unit with door (standard hinges). It looks like they installed the cabinet first, and then fitted the boiler, as the flue goes through a hole in the unit. They've done a little bit of a a botched job because the unit is not fixed securely to the wall on the upper right. This means that it comes away from the wall by about 5-6mm, meaning that the door will not close correctly. What I am looking for is a solution that enables this unit to be fitted securely to the back kitchen wall, so that the door closes properly. I'm not able to do this as I don't have the right tools, and also I'm not sure what the right solution would be. It isn't possible obviously to remove the boiler; also, the kitchen unit is secured in place around the boiler (see pictures), so any fixing solution would have to work around these factors and the restricted access. I assume there might be a variety of solutions (screws, adhesives, brackets), but I'm looking for a trader who can provide a solution that works without requiring any major dismantling and suchlike.
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