We use one throughout the summer months in the basement to keep the musty smell down with the increase in humidity. Obviously, living as I do in the U.S., I can't help you with the brand, but de-humidifiers all work the same way and are quite simple. Here, one can buy a standard model for about $300 U.S., so you can do the math for expected price in pounds considering the exchange rate. You could spend in excess of $1,000 though.
They aren't very quiet. You'll get used to it after a while. They don't
roar. but the constant fan noise is noticeable. The constant emptying of the tank that collects the water is a pain in the tush. You'll find that it probably does better if you run it all the time, rather than just when the bathis being used. Is the bath equipped with an extractor fan? if not, see about installing one and if you have one see about a model with more volume.
Be sure to check the
pint per day rating, which is the expected amount of humidity the machine could extract. Probably not less than 35 to 55 is about right for a standard bathroom.
Here's a link for U.S. brands to check operating statistics... Best of luck!
http://www.nextag.com/dehumidifier-basement/se arch-html