Only a £2000 PC? Mine cost over £3,00 and that was before I added my monitor (a Dell 3008WFP)....
As this PC is about twelve months old it's not going to eb the best out there - I don't claim that.
Just because you have spent a lot on a PC does not mean that it can run a game that dates from 2004 with everything set to the max.
RTW does not use any more than one core - anything else is wasted.
RTW does not make the most of recent graphics cards - they simply have feastures that are not utilized by such an old game.
It's a matter of following advice from other people to get the most out of the game with the PC you are using. If you don't follow such advice then you're likely to suffer random CTDs.