That's grimy, those ones definitely take ages. Had one last week that hadn't had a service in the 12 years its been fitted, was an absolute state, especially as the ceiling had come down at some point and the expansion vessel at the back (ariston micro genus he, so its exposed) was covered in huge chunks of plaster, that was fun to replace. The inside was also full of grit and flies and the heat exchanger was nasty. I should probably charge a bit extra if they haven't been serviced in 3+yrs.
Is the portable power washer in the picture good? Haven't seen one of those before.