I have been most content with the products from major, long-established UK manufacturers with a well-known brand name.
Twyfords, Armitage Shanks, Ideal Standard. You can still get pans with a BO if the soil pipe exits vertically through the floor rather than horizontally through the wall. you need to measure the spacing accurately to try to find one that fits.
Armitage are particularly good for old-fashioned styles used in restoration of period homes, retro hotels etc.
perhaps there are some good products by anonymous imports sold cheap in the sheds, I don't know.
You can still get the Twyfords catalogue, although the company has been bought by Geberit, and products are being rebranded.
If you find you have a pan with a poor flush, a couple of easy fixes that might work:
check the water level is adjusted as high as it can go without risk of spillage or leaks from the openings in back, side or front. The overflow pipe might need to be adjusted. in some cases plumbers cut it short which prevents you increasing the water level.
fit a "flapper" flush valve which gives an excellent gush of water.
If dual-flush, use the "big" button when you consider it necessary.
A few homes from the 1980's or earlier still have a "syphonic" pan. These can be restored to working order with a new valve, called a "bomb", and are highly prized by those in the know.
I bought one for my first house, and it cost more than the rest of the bathroom suite put together.