A friend of mine did our bathroom (he's a bathroom fitter) - spent 4 days just planning the tiles.
Bathroom was a back to brick job so new boards etc were needed. Again time spent here making sure they were nice and level meant the actual tiling went much more smoothly.
If you're doing the floor as well onto wooden floorboards you need to put down some Hardebacker boards and then join the boards with concrete paste so the whole thing becomes one 'slab'. Any individual movement will cause the floor tiles to pop up.
Oh and he was delighted that we chose 900mm X 300 mm porcelain tiles weighing about 8kg each - absolute pain to work with.
He did a smashing job - nice centred grout lines which line up right across the room etc.
Could I have done it myself? Possibly. Would it have looked as good? Absolutely not and having seen the amount of work that went it to it I'm glad I got someone in.
Done 3 walls (which is half the bathroom) so far and a work in progress. It was easy enough when I got going, but a pig to start - and I hate grouting. Would a professional have done a better job? Yes, definitely - I'm happy with my efforts though. The effect of the tiles is uneven, so I didn't have to get every single edge flush.
Definitely start one row up and regarding an electric tile cutter - only use for awkward cuts - for straight cuts, a scribe/snap cutter is much easier and quicker
[url= https://farm5.staticflickr.com/4489/23499376098_d60a388770_h.jp g" target="_blank">https://farm5.staticflickr.com/4489/23499376098_d60a388770_h.jp g"/> [/img][/url][url= https://flic.kr/p/BNyrNS ]2017-09-27_01-42-28[/url] by [url= https://www.flickr.com/photos/85252658@N05/ ]davetheblade[/url], on Flickr