can you advise me on what visa do we require and the cost of same for our visit to china? thanks

You two should apply for L type for your visit to PRC. The Chinese embassy doesn't publish its fee table on the website. So you will learn about the costs when you apply for it. For the L type, you two should provide round-trip ari tickets and hotel bookuing in PRC. If you have an invitation letter, the required air tickets and hotel are not required. By the way, your wife should provide her original and copy of her valid resident permit in the Ireland.

Other required documetns are your passports, finished application forms together with your recent six month's photos.