This is a very complex area and, as it happens, Abdul's suggestion may not always work.
Just to clarify "reverse charge"; if EU companies transact services across an EU border, eg you (in the UK) buy a service from a company in Ireland, the services is deemed to have taken place in the customer's country and so, there should be no foreign VAT charged and, as the supplier is unlikely to be UK VAT registered, it will not charge UK VAT either. So, to kick off the UK's VAT trail on the service, the buyer (you) records both a Sale and Purchase in your UK VAT return, as described by Abdul above .
In the circumstances you describe however, the supply is actually taking place in France and, almost certainly, you'll have suffered French VAT and so this is not a reverse charge situation. Instead, I'm pretty sure it is outside the scope of UK VAT and so not recorded on the return. You may however be entitled to make a reclaim of the French VAT directly from the French VAT authorities.
More details are on HMRC's website: http://www.hmrc.gov.uk/vat/managing/international/overseas-traders.htm
Please note that as Clear Books is not authorised to to give direct tax advice the above is my personal opinion as an accountant and so you should always double check the entries with your accountant or HMRC.
Hope that helps