If you're 100% about going for the fATPL and have the current £317 to spare, plus travel arrangements/costs to Gatwick, then I'd say why not? As has been mentioned, at least then you know you're not going to be tripped up by not being fit enough to fly commercially. Or, don't, it's really not that much in the grand scale of things
Re: The Class 1 certificate, how do you know if your hearing is up to scratch? With the eyesight, you pretty much know if you're within the range specified. I'd assume that as a (presumably) healthy 22 year old male, I shouldn't have much to worry about on the hearing side of things, but then I have been to a few loud gigs that have left my ears ringing for a couple of days a few times. Makes you wonder!