Have you tried to use a surface cleaner instead ? You will find with one of those you will have a lot less splashing.

Also you could try using a garden fork to force holes all along the area where you plan on pressure cleaning to help drain the water down into the soil

Thanks Gav- I see Karcher do a surface cleaner attachment which sounds ideal. I'll also try the fork suggestion.

Cheers
Scott

The surface washer will probably be the best solution as you will have no splash back and the excess waster should just roll out from under the cleaner and flow down to the lowest part of your garden.