When I lived in Devon, I had five acres of bramble that was 5/6foot high.
I used a brush cutter and made small fires after cutting it up.
Then I used roundup weedkiller on it.
Went over and over it several times before killing it all.
Took fcukin months to do.
But eventually won the battle of the bramble and 6 month down the line with alot of work. Reseeded the area over and over. Within the year I had the horses grazing on the area that was bramble.
The hard work will help you lose those extra inches around your waist line.