This is an often shared top tip, also in the top tips section...
As helpful as you're trying to be, it's in the wrong section, and has been posted numerous times in top tips before
Also, not all of those premium numbers have an alternative 'free' number. They're also not 'free', they will come out of the goodybag or credit you've already paid for
The app WEQ4U is also great at coming up with alternative numbers. Personally I never use the queuing feature on it, but I find it easier to simply type the 0845 number in to the app and have it call the geographic equivalent, than search on saynoto0870, then copy and paste into the phone dialler.
all the best