OK...
First of all, you will get into trouble for discussing shooting live quarry of any type with pistols here, the general consensus is that pistols are not accurate or powerful enough for humane kills, important even for vermin.
I love Tempests, own a lot of Webleys, and really enjoy them. I lubricate mine with Moly grease and Moly GN Paste, and only wipe over with oil. If you do the same you will find it gets more enjoyable to shoot, smoother and with GN Paste on the trigger parts the trigger will also improve. You may find power improves a little too.
Finally, give Milbro Caledonian Ultras a try, they're good pellets and have assumed the place that we all used to allocate to the original and best Ely Wasps, in my opinion any way.