I think box AP is for French pensions, and will attract other social charges.
For several years we have done the following without problem (my university pension and my wife's state pension):
Obtain/download
Déclaration des revenus encaissés à l'étranger 2008 (no. 2047-K; the K is optional depending I think on being printed or online)
On page 1 fill in the value(s) for Vous and for your Conjoint under Pensions, retraites, rentes.
According to Siddall's you should use an average value of €/£ of 1.258 for 2008. Also fill in the country where the pension is issued (I am assuming that all this is for the UK).
These amounts are then re-entered in the main Déclaration for 2008 (form 2042) in box AS for you and BS for your spouse/partner.
If you are doing gîtes / chambres d'hôtes then there is another complementary form to deal with.
I also recommend trying out the declaration and doing a dummy calculation:
http://www3.finances.gouv.fr/calcul_impot/2009/and see whether the tax predicted looks right !