I too am a qualified plumber/part 'p' spark,I do all my own alterations e.g .knock walls through/construct walls,plastering,carpentry,wall and floor tiling etc. most of these trades were self taught through trial and error,e.g. I boarded garage and plastered and plastered, I admire your willingness to work for nothing to gain experience,I too did this, but be careful manya person wil use you for ages teaching you not (hopefully not here lol). I did it this way because you get a plumber in to do first fix then you fit your tiles then plumber comes back and hopefully iit,s as smooth as that,in reality it isn't andyoulose money waiting,same goes for other trades .if you can do plumbing and tiling that's twice the potential of work,if you can fit a. Bathroom and tile it saves the customer havingtofind other trade and you can jiggle things round to suit and a continuance of work.hope this makes sense to you.take your time at tiling ask advice,plenty available inc. at some tiling shops and enjoy.