So, my 349's front drum brake is a bit of an issue - never caused problems in the UK but it's a bit of a liability here when you can have long steep descents that go on and on.  Basically, although it's clean and the shoes have lots of decent looking material left on them there's no bite (more of a gentle slowing suggestion), and the lever action feels super spongy despite a new cable.

Before I think about getting new shoes, are there any tricks I can try to wake it up again?

Have you '' seated '' the shoe properly ? What you describe is the same as I felt on my TY. The shoe where touching the drum only one spot.

Guy

Chamfer the leading edge of the shoes with a file.

If the drums well worn, new standard shoes won't make a huge difference. Get a pair re-lined with oversized material. 

Try loosening the front axle & tighten it back up while holding the brake on, that will centre the brake to the hub

Best braking out of your drum involves having the shoes turned to the exact size of the drum, normally easier to do with new shoes

Glaze bust the drum braking surface. Use wet and dry 600 grade and a little water. Rotate the rubbing action around the drum to produce a clean grey effect on the surface. Clean thoroughly with damp cloth. Don’t chamfer the brake linings too much as this reduces contact surface area. They should already have a very slight chamfer which just needs cleaning lightly with fine emery cloth or scotchbrite pad.
Montesa front brakes (348) are quite good when compared to Ossa-Bultaco type.

Tony27 method is an excellent way of centralising the brake plate?  

Cool, thanks for all the tips, guys!  I'll start with the easiest / cheapest ideas first, and work my way up ... I don't think the hub is terribly worn, but will have a more thorough look when I pull the wheel

The best way to '' seat '' the shoe in the hub is with chalk. The subject as been discussed many times here.

Guy