I am usually very pleasant to check in staff, very polite, have everything they need ready for them and then I enquire are you full or is there any chance of an upgrade please, works in th US or in larger hotels not always possible in the smaller rooms. If you are unhappy when you get to your room, leave luggage there and go back down, wait patiently to see the person who checked you in and explain nicely and quietly [ they dont like other guests to hear] what the problem is with the room, loudly complaining wont help at this stage.
Trouble is that most Brits hate to make a fuss and put up with almost anything, so thats what gets allocated to them.
If this doesnt work and you are still not happy demand to see the general manager not the floor manager and really go to town with the complaint [ no swearing it just makes you look second class].