Hi PAT,

1. In principle for the purposes of British Citizenship application it makes no difference that your current Philippine passport is expired.
However take notice of this on the application form:-

SECTION 1 Evidence of identity: required for all applications
• *Your passport OR
• *National identity card OR
• *Home Office travel document OR
• *Home Office entitlement card OR
• *Home Office ARC letter OR
• Your birth certificate OR
• *Your driving licence

*if you used one of these documents when you took the Knowledge of Life in the UK test you will be expected to use it again by
enclosing it with your naturalisation application.
If the name you are currently using is different from the name on your passport or travel document you should send evidence of
the change of name
2. Personally I tend to agree with sars, it's never a good idea to have your passport (best ID and only travel document) not valid.
Plenty of people get caught out that way.

When are you eligible for British Citizenship application ?

I feel you could get your passport renewed fairly quickly.
My only concern is that you would be without any travel document until you either renewed the Philippine passport or until you received a British Passport. The latter could take quite some time.