If you don't renew expired ratings, they will be printed on the back of the licence, and you can renew them later. You will have to re-apply to the CAA to have them transferred to the front of the Licence before you can use them again though. (For a fee of course!)
LA you have misinterpreted the information. MJ is correct.
At the point of conversion, any expired ratings will be placed on the back of the licence. In order to move them to the front of the licence and into Section XII will require CAA action - which will cost you. An examiner in the field cannot do this.
The recent change allows an examiner to sign a rating which is contained in Section XII and has expired, regardless of how long that rating has expired.
Therefore, I would recommend you renew your SEP and IMC then convert.
ifitaint...