Richie,
All of the major chains have locations in Liverpool ( i.e. Radisson, Marriott, Hilton etc ) and normally offer a 50% discount. With discount you are looking at about GBP60 a night. Its probably cheaper out on the Wirral but it really depends what you are going to do as to which is the better location ... the Wirral or Scouseland central !!
You may get a better rate at one of the smaller independant hotels.