Firstly, thanks for all your help. Extremely useful. Personal experience
tales are for more persuasive and informative than glossies from mfr.

Long (very long) term I'm maybe going to look at a CNC system. Seems
eminently sensible but yet a further step away from the "hearing the swish of
nice curly shavings being formed while listening to birdsong," doing it for
the love of it approach. Me? I love routers and I think it's O.K. to use
metal fasteners in joinery so I'm not exactly purist about using hand tools
with wooden blades and violin-peg adjustments and I actually like machine-cut
dovetails (I think a hand plane is perfect for peeling apples and mangoes...
) I really really appreciate traditional cabinetmaking, but personally I'd
rather put time into rewriting software than serving an apprenticeship under
a master joiner.

Anyhow

After long and careful deliberation, reading everything I can find and
surfing till my eyes bleed, I've ordered an Incra Sys25 with wonder fence.

It's WAY above the budget, but I've robbed my daughter's piggy bank, torched
the outhouse for the insurance money, sold the family cat into white slavery
and agreed to be the bitch of the head of the local mob for the next
seventy-five years. Oh - and I swiped money from the
fix-the-kitchen-afer-the-ceiling-flood fund so the plastering will have to
wait. I think we'd all agree that that is a legitimate appropriation (think
new kitchen cabinets etc. :-) )

The scheme:

Having learned that it takes about 20 seconds to line up with a saw blade, I
intend to use it as a portable-ish fence for the lousy-cheap TS as well as
for routing, hence the 25 not the 17 inch version.

I can mount it on a clampable baseboard, Option #1

I can screw angle iron to the lousy-cheap TS and add extension wings - router
insert in the left-hand wing, Incra device on the right (movable leftward as
needed) Option #2

OR

Option #3
remove the tiny aluminium table from the lousy-cheap TS and then bolt the
rest of the TS assembly directly under a sheet of Formica'd ply or mdf, which
would then become the much bigger, smooth table top for both the TS and
router.
The saw has an 80mm max cut at 90°, so I could afford to lose a little of
that, I think. Additionally I could then make drop-in kerf plates to give me
zero clearance for whatever angles I'd use, which would be a huge improvement
as the lousy-cheap TS has a paper-thin metal plate with mountings that only
allow paper-thin replacements and a has huge gap which swallows any thin
sections I try to cut.
I' d probably laminate the top up from 2 or 3 sheets of 12mm (mdf?) going
down to single sheet over the lousy-cheap TS with strengthening battens
running full length and widthways. Again I'd value opinions on the scheme. I
don't think it's dangerous in any way - it's not like mounting an inverted CS
on ply, for example (Yikes!!!!), and all the TS mechanism should remain
intact but there might be a problem I haven't thought of, which is why I'm
running it past you guys. I realize it won't be as flat as machined cast
iron, will have more friction and I'll lose some depth of cut compared with
bolting on wings or dropping the _whole_ TS, complete with original top, into
a cut-out in a big sheet.
It WILL, however, give me much greater table width, safer kerf plates and
even a little more in and outfeed surface. I'd probably not use a mitre slot
as such but use a sled sliding along the Incra face (maybe adding a slot in
the sled's surface if necessary?)

Most of the bits are available individually as cheapos, apart from the 3/8 7°
which can come from either CMT or Trend, so that's a worry out of the way.

Phew!!!