Hi,
Firstly when researching what you want in your bathroom always ensure that your aspirations will fit so measure up and make a scale drawing and slot in the appliances bearing in mind the position of your soil stack and supply pipes ect.
when choosing your appliances always go for someone who has BSEN certification on the equipment and WRAS approval of the brasswares, this way you know they reach a minimum standard. Myself I choose equipment from Bathco in kings lynn but if you go to a main supplier to the trade like PTS & Plumbcentre you wont go far wrong.
With baths i always go for the thicker resin baths or the pressed steel baths, pressed steel baths cool down much quicker in use due to the conductivity. Shower trays i always go for resin capped stone trays the heavier duty the better many plastic trays are very thin where the waste outlet is and can crack in use as they flex so the heavier they are the less likely to flex and will last longer.
Fitting the shower is relatively easy depending on the waste position walls will have to be prepared and maybe water resistant plasterboards installed then the tiles.
With showers again go for a reputable make like Mira or bristan.
Moving the rad is fairly easy depending on your system and the position you wish it to end up in.
When talking to your fitter you want to look for someone who will cover all aspects including building, Tiling, Electrical & of course Plumbing, if they subcontract these services then thats ok but make sure that thier quote is all inclusive, Whoever you chose should be in overall charge so you are invoiced by one person and he takes the responsibility for anyone he has in his employ.
Lastly its a good idea to make sure you have evidence of current CRB Criminal Records Branch Checks in place, all reputable firms will have this.
Many Thanks