You shouldn't pay less than euro450-500 for a cavalier as any good breeder doesn;t charge less than that; unfortunately many backyard breeders and brokers (sellers of puppy farm puppies) also charge that much, typically in small ads or the Buy&Sell (definitely don't buy a dog from the Buy&Sell).
There are some cavaliers listed free to good homes there at the moment -- normally I would call and try to get them into rescue but I don;t have the time to do that right now before I go away for three weeks. You can also fill out a rehoming contract and I can add you to my list for adults coming into rescue; this requires a homecheck and a rehoming fee to cover any medical costs (typically a vet check, perhaps vax and neuter, which are costs you'd have anyway).
This is a breed with a lot of health issues and the chance of having them is greatly increased by getting dogs bred by backyard breeders (people who just breed their own dog with no regard to matching pedigrees properly to breed around serious health issues) and puppy farms of which there are many in Ireland. A lot of them are out west, so be very, very careful buying a dog.
The best thing to do is contact the breed club (I provide a link in the Breed rescue listings or see ikc.ie under the 'buying a dog' heading I think) and ask them for their puppy listings. They can tell you which breeders have litters. Always ask to see at least the mother, & go to the breeder's house -- if they offer to bring a pup to you it is almost certainly a puppy farm puppy being sold by a broker. Though these dogs may cost slightly less up front (usually they are the SAME asd a good breeder's pups) they will likely cost quite a bit in the longer run due to health care expenses.
I strongly recommend getting pet insurance thru Allianz as it is not very costly and most cavaliers will eventually be dealing with heart problems as they age.