There are generally far fewer CMV negative donors than CMV positive donors, whichever sperm bank you use - just because they are less common in the general population. If you are doing tx in the UK and require a CMV negative, ID release donor, it might be more of a case of finding the donor you like first, then looking at the price/ sperm bank. (I am CMV negative and had to use a CMV negative donor - I had tx abroad and ended up using an anonymous donor as the sperm bank had no CMV negative, ID release donors that matched any of the characteristics I was looking for at the time I had treatment). As far as I remember, ESB has an extra fee for the UK as others have already said - not sure if this is still the case but worth enquiring about. Good luck!
Rose xx