It all depends how much time you have. I like trawling the net for stuff (am about to do a kitchen extension so have spent months researching everything from worktop, dishwashers, ovens, hobs, microwaves, glass splashbacks, flooring etc)
We did an en-suite a couple of years ago, new quadrant shower cubicle, electric shower, toilet with concealed cistern, sink, towel rail, re plastered whole thing, flooring and tiling for under £2k, we fitted it ourselves and got an electrician to connect the shower. Plasterer was a professional too.
I don't believe in spending huge amounts of money for a brand name as other products are just as good. For example the flooring was B&Q value range vinyl planks. It looked very expensive when it was down.
We only tiled the shower area and behind the sink (it was previously tiled floor to ceiling and made the room very cold)
If you want someone to do it all for you from purchasing to fitting then it will cost you lots more money.
I got all of my bathroom on line and got the plumbers/tiler in afterwards and spent about 2.6k in total for a big shower, double sinks and a free standing bath. You get more choice on line anyway I think. Just make sure sinks have the right tap holes for mixer tap if that is what you want!
We bought all the stuff to save on anyone else taking a cut & were able to make considerable savings on list prices of the fittings by negotiating. It was a bit of hassle running around getting everything - even the grout etc. but worth it to save some money. We are so pleased with the end result.
We've just had what sounds like a very similar job done. Ours was £2000 for the work (which took one person 3-4 weeks) plus fittings, tiles etc. We did go for v high end fittings, expensive tiles, underfloor heating and a custom made glass shower door due to sloping roof & I think the total was about £7000. We were quoted £8000 by someone else for much lower spec & £12000 without tiles (which were about £800) from a posh bathroom company. Cost us a lot but it is exactly what we wanted & we won't be doing it again!
I know it's hard to say but we are looking to completely gut our downstairs bathroom. Will need a new shower (taking out bath) and new toilet (concealed cistern), new sink, fan, lights and all tiled. Got one company round who has said starting from £7000! Am horrified as hoped to get it much cheaper than that!