Setting Out Tiling a shower

[amyL]

I have a 995mm x 995mm built in shower in the corner of my small bathroom. The the mixer was not centred properly on wall, so it sits a little off centre. The genebra and shower rail are on the adjoining wall. Should I centre the mixer on the one wall within the 600 x 300 tile and tile outwards from there? The just carry on so the shower rail may sit on or close to a grout line, or should this be centred as well? Is it better if doing a brick pattern to have a wrap around effect ie half tile on one wall should half tile on the adjoining wall (not start off with a full tile on that course).