Don't bother with the glyphosate, it won't kill brambles - your first suggestion is the most appropriate - cut off all long growths as low as possible, then dig around at the base of each plant to expose, hopefully, a knobbly, woody base - make holes about quarter inch deep with an appropriate wood bit and fill the holes with SBK, without spilling it anywhere else, including on yourself! Cover with something like an upturned pot and replace any excavated soil.

Ok, thanks bamboo. Is SBK the best all-round weedkiller in your opinion?
I was in the garden centre today and was going to buy Glyphosate but thought i'd ask on here before spending any thing, glad i did, if it is i'll get the more expensive concentrated bottle of SBK, that should last a while.

I didn't realise they had an unconcentrated one! I just buy the ordinary SBK that you're supposed to dilute, but I don't, I use it neat, but very carefully and sparingly. As for whether its the best herbicide, that's the wrong question - its the best for woody based plants such as tree stumps, bramble roots, etc., but I wouldn't use it in a spray on foliage, there are other weed treatments better suited to that, so it rather depends what it is you want to kill as to what the best solution is. If you've got a Wilkinson store anywhere, its cheaper there than the garden centres.

As helpful as ever, bamboo, have a good weekend.