Hi JMan.
Real low end and good overall quality is near impossible to find for £250.
Audition the Mission M35i, people might post different opinions, but at least put them on your shortlist..They are over your budget, you can get them for £300 to £350. These will go loud and generate nice lows and they also sound fantastic overall.
What the human ear can not detect (low end wise) you will feel.
There are not many, if any at all, (but i could be wrong) floor-standers in your price bracket that can achieve the low level information you want and maintain a good presentation of sound.. Speakers to fill that criteria are usually just made to go loud and will easily fatigue the listener after very short listening periods.
Good luck with whatever you decide on.