Update:

Using Daystate Heavies I have been getting a single hole group at 30 metres. However due to the lack of availability of these pellets I have now swapped to Daystate Sovereign Rangemaster in 10.3 grain. These have given a power boost to 11.6 ft lb, accuracy I will report back on later.

Apparently H&N FTT in 4.52mm are also very good in these. I will stick to the Sovereigns at the moment due to getting 1000 of them for Christmas.