I'm also lactose intolerant , and I can use ON whey , but I don't have any problem with trueprotein whey protein isolates , I used CF and CFM WPI , without problems , also i don't have problem using complete milk diary isolate , so if I can use them , and as I can see my intolerance is worst then yours , so you won't have any problems with WPI , since I don't have any problem , and trueprotein WPI is way better then ON whey
also I tried hydro whey , and pepto pro , I can use it without any problem
hope this helps , I had same issue with my first , and I have high lactose intolerance , and I can say before I started ordering from trueprotein , only protein powder that I could use , because of my lactose intolerance is ISO-100 , and I tried most of protein powders , even ON whey and I had problem with it , then I ordered from trueprotein and from that time , more then a year , I only use trueprotein protein powders , so like I said , don't worry just order , you wont have any problems with WPI CF for sure , also other WPI , but I would suggest WPI CF with premium flavors