Painting glyphosate onto cut stem(sealed with sellotape+plastic bag)

Sounds long winded - just dig the * up!  

I did read once (can't any more) that you put rubber gloves on pour glyphosate on them and wipe them over the weeds leaves. Supposed to work!!!

Sounds to me like you are trying to over complicate matters. Dig out what you can, then go over it a second time, again if time allows. It will be easy second time round.  Early next spring you can go over it again, digging in manure etc.  Any new growth will be easy to get out.
The trick is to not let the weeds get too big before you dig or hoe, that way they never get estabished and become a big issue.

I think your right, i will save it for early in the year if needed or just use it to spray some plant that has taken over the back of my garden

I have read that people make a mix with a bit of wallpaper paste which makes it easier to paint onto the plant.

Damn! Spent my round up budget on a watering can version rather than the one with the pump spray! Would a regular sprayer work? Apart from giving me hand cramps obviously.

Yeah thanks Yorkie,  would do that as a matter of course - gonna do a test strip tomorrow. See if it's effective on the short stuff (thats still sprouting this late in the season!).

When it comes to the couch that's up to waist height, I'll use the watering can and spray a bit later with my top tip of adding a teaspoon of milk as a cheap surfectant!