Thanks Char.
Also found this on AN Naturalisation guide.
Travel after submitting an application After submitting your naturalisation application, you are free to travel whilst you are waiting for a decision using your valid passport and evidence of your valid ILR, or other
valid status. You do not need to tell us about your travel plans.
Please be aware, however, that you will usually be required to enrol your biometric information within 45 days of submitting your application. This may involve attending an appointment at a UK Visa and Citizenship Application Service (UKVCAS) Centre (operated by Sopra Steria) in person and failure to do so would invalidate an application.
You will receive instructions on how to provide your biometric details once
you have submitted your application.
In addition, please note that should we grant an application, there is a 90-day period
where you will need to arrange attendance at a citizenship ceremony.
But, outside of these timeframes, there is nothing in the citizenship process that would
prevent you from travelling while your application is being considered.
Please bear in mind that a naturalisation application does not provide you with
immigration permission and you will need to demonstrate your entitlement to re-enter
the UK at the UK border. Also, a lengthy absence from the UK could cast doubt on your future intentions.
https://assets.publishing.service.gov.u ... _06.07.pdf