Cornish,
sorry to hear of your problems. I have been fortunate that most of my stuff has worked on a PnP basis. Old netgears and current BT kit all appear to work fine on a pnp basis, and my knowledge of techie is only marginally above zero.
However, I do echo the earlier comments about local help. My local IT helper normally does what is required on a single visit, at most 2 visits, and he charges about half what the plumber does.
Don't use the helpers/experts from the big stores - they are way too expensive.