Hi John. Excuse me for butting in, October last year I bought the same rifle a full length HW100 in .177, although I found they are not overly pellet fussy as some may think, it is worth trying a few different types/brands of pellets. This guy on eBay sells a small number of each, so rather than have the expense of trying full tins at stupid money each, you can try loads at pence each.  Seeing your mostly target/plinking, Falcon Accuracy Plus are one pellet hole groups at 20-45 yards for me. 
http://www.ebay.co.uk/itm/331481087952?_trksid=p2060353.m1438.l2649&var=540652463206&ssPageNam