Any loss of staff as a result of installing self-service checkouts into what are pretty small stores; Aldi, Lidl, and Co-Op (especially) would result in minimal loss of staff if any. The teams are not very large to start with and there is little room for manouvre, they might take out one low number part-time role at worst.
In very large footprint stores (100000 sq.ft - not too many this size in the UK but they exist) where staff numbers would be up to around 1200ish then a big bank of self service tills installed might cut (plucks figure from air) 10 jobs which is a negligible percentage.
Staff reduction is currently the name of the game in UK supermarket chains as they are one heck of a cost in what is a low margin business. The real reductions being made in store management costs and positions formerly involving a level of expertise.
Both ASDA and Tesco have massively overhauled their instore management team structure with reduced numbers and greater spans of control.
The above two retailers plus
Morrisons (I don't have any contacts in Sainsbury) are also furiously closing the various fresh food counter offerings primarily as they are expensive to operate in terms of staff cost, plus the trades of butcher, baker (no candlestick makers!), fishmongers etc are dying, ergo difficult to recruit from a diminishing pool of expertise.