Get a big brand bog.
There are lots of unbranded ones at modest price and people moan about how poor the flush is (modern WCs cisterns have low water content)
I find Twyfords very good. I got an E100. Syphonics appear to be unobtainable as they use more water. A hundred pounds extra on the price is trivial over the years it will last. They have been bought by a German group now. There are a few other big British brands. Armitage Shanks look old fashioned to me.
If you are getting white they do not have to be the same brand.
Plastic baths are very feeble. There are a few brands that make reinforced plastic baths (very heavy, gave me a hernia). I recommend Carronite. You will have to order it, they have a good range of sizes to order. Get heavyweight bath panels (you can get matching reinforced ones, they are very difficult to cut to size) or painted chipboard ones that are cheaper. The thin plastic ones are rubbish and will crack when you lean your knees against them. Do not let the bathroom fitter glue the panels into place.
Pop up wastes operated by a knob on the overflow look nice but leak or break, and are difficult to replace.
I would avoid basins set into a cabinet, the cabinets are prone to water damage.
DON'T have a cabinet or shelves over the basin. When a glass jar or bottle falls out, as it will, the porcelain will be cracked. Have the largest possible mirror on the wall to accommodate people of varying heights (tilting mirrors are a nuisance, and go wrong) and your shelves or cupboards to the side.
High street Bathroom showrooms are handy for people who have lots of money to throw about.
If you have a hot water cylinder you can have big taps. If you have a combi, you can't have such a good flow. If your hot and cold taps are different pressures you must have separate taps, not a mixer.
Chrome taps and fittings last a long time. Gold or painted ones don't. I like Bristan. Ceramic taps wear out, so buy a reputable UK brand or get some spare cartridges. Tap washers are cheap and easy to replace.