I know this thread has been up for a while but...

I've used voiptalk.org for my outgoing fax line and haven't had any failures, so perhaps it's come of age. It's routed through a Fritz!box wirelss router which is ideal for a SOHO.

For incoming I use a faxtoemail service so I don't get spam faxes and don't get my faxmachine ringing in the house in the middle of the night (that said you can set up the Fritz!box to stop calls at different times).

I've tried a few services and have voiptalk 0845 (£8 to set up then no ongoing costs), but as I also want people from overseas to be able to fax me I have a geographic number from TTNC.co.uk (£25 to setup then 5p per minute for incoming faxes). Another possibility is flextel.ltd.uk who don't charge at all for 0844, 0845, 0870 or 0871 fax numbers. Don't know how they do it but they've been around for a while. There used to be a lot of operators offering 0870 faxtoemail but the OFTEL ruling forcing the cost to be reduced these have mostly stopped being offered.

Hope this helps.
Colin