Artificially introducing dung beetles to a grassland in the UK is not viable for several reasons, including the fact that you would have to disturb and impact populations elsewhere.Many species are threatened so shouldn’t be moved and it can be difficult to identify species and not accidently disturb threatened dung beetles.Also, a natural population will have a far greater long term success rate.
The good news is that dung beetles fly, so given the right conditions they should naturally populate your grassland. There is no conclusive data as to how far dung beetles will fly, so having neighbours who have dung beetles will really speed up the process.
First off, they will need dung, which means livestock. If you are becoming more extensive with zero inputs, then you a heading in the right direction. Having dung out all year will also help support ongoing dung beetle populations. There are lots of other recommendations on the website as to what else you can do to help.
It would be worth doing some flotation tests
of a dung sample plus a trowels depth of soil from underneath the pats in May/June to just double check you don’t actually have dung beetles already; you may get a pleasant surprise!