I'm in exactly the same position, although our management systems havnt been accredited yet.
I've combined our seperate safety, quality, and envirinmental management systems in to one now, which was quite a simple task.
I'll be looking at an external gap analysis shortly which may or may not throw up issues prior to us going for the accreditation.

If you want to fully integrate you should use PAS 99 to set system structure. I would suggest a 'combined system' rather than full integration as this will simplify your future external audits i.e. as soon as you state that you have a integrated system then you will be audited against the requirements of PAS99 (certainly with BSI) and the other standards to which your organisation subcribes. With a 'combined system' you will just be audited against the standards.

Also, just being pedantic but organistions that successfully attain external verification by an accreddited body such as BSI, SGS or Lloyds etc to a standard such as ISO9001:2008 do not themselves become accreddited. The correct terminology would be 'certified' or perhaps 'registered'.

GC