I don't know if this will help anyone but the Bosch aquatack 115 is reduced at Screwfix from 139 to 89 gbp, IIRC.
I've read the excellent pressure washer faq, I think written by the medway handyman.
Based on the advertised pressure of 115, which I appreciate is probably the rating of the safety valve not the operating pressure, the equation in the faq gives a result of 1.2, which falls between ok and reasonable. I don't know whether the insides are plastic or metal; does anyone else know?
Bearing in mind the real pressure is likely to be less than 115 bar in use, which would make the result nearer to "ok" than "reasonable", is it that much of a bargain? Or would it be better to get a higher spec'ed model?
After reading this line in the faq: "Hire shop machines are going to be about 2.3, just about the most powerful motor you can run on 230 volt single phase." I started looking for such a beefy machine, thinking it would be nice to buy the best I could but they seem to start at about 300gbp, which is a bit expensive for a once a year patio clean ;(