Why does everyone always think in terms of worst case scenarios? It's usually the daft, simple things that go wrong. It is possible that some extraneous article has got into the machine and is whizzing around in there. This would not only make a noise but it might also cause the machine to work inefficiently. If you go to
http://www.bosch-home.co.uk/quick-links/custom er-service/download-product-manuals.html this will tell you how to remove the bottom front panel to get access to the area where all these thing accumulate. While you are in there you should also clean out all the gunk that has accumulated over the years.
My daughter's Bosch washing machine made a vibrating / whizzing / clattering noise and she managed to follow the instructions to get into the sump where she found not only a piece of support wire from a bra but also a pound coin. She then reassembled everything and the machine now works perfectly.
So you will not only save money by doing it yourself, you might even make a profit!
You can bet if you call a plumber out he will fit new bearings and a new drain pump and anything else he can think of.