have a look at www.JSB-Diabolos.de
for pellets including the mix packs at good prices and v good service. Cheaper including postage than you can get over here. Olga will also sort out batches once you find the ones you want.
Issue with the mix packs, is that they do not quote full batch numbers from memory so you can get sizes but not actual batch level testing.
My Walther liked JSB heavies at 4.52 - but it is an endless pursuit so good luck !