.. Or anyone with more sense than me!!

Been wanting to get a electric shower put in at my house (the plastic thing attached to the taps, just doesnt do the job ) anyhoo's was reading up and it said i couldnt have a eletric shower as i have a combi boiler.. I had to have a mixer or shower tower (never even heard of one of them lol)

Are these expensive.. and how much am i looking at, at paying for this kind of job?

Thanks in advance!