That's the way it is no. You might get credit here for CGT paid in France but it isn't definite. You need to query this with the Revenue and/or a tax advisor.
The Double taxation Treay is being re-negotiated but there is no indication of what will be in it nor when it will be finished, ratified and brought into use.
For info, if you keep the property in France for 15 years, it will be free of CGT in France - you get 10% relief per year each year from year 6 of ownership. (Sorry, that doesn't seem very clear)