I would certainly suggest cutting your own mounts, but not to get involved in making frames as the equipment to do it properly is very expensive, large and heavy.
As ks suggests you may be able to strike a deal with a local framer, and one way to keep costs down even further is to buy lengths of your preferred moulding (eg. Arquadia or D&J Simons in London) and get the framer to make them up, with glass and backboard.
Youâ€™ll need a point gun, and the basic Tabmaster is cheap and works well (shoots both rigid and flexible points)
Ikea Ribba frames (in a variety of natural woods) are quite nice and well priced, but of course only come in a few sizes.
Back to mounting: 1500 micron archival mountboard bought in packs of 10 from the suppliers above work out at about Â£3 each.
For cutting mattes I would recommend (in ascending price) the Logan Team system (various lengths; just a straight edge with sliding bevel cutter), Longridge (bit more sophisticated), or if you really want to splash out, a KeenCut - I have the Artist Plus 1200, and very good it is too ...or you can spend Â£20k on an automated laser cutter