I’m aware that it’s illegal without the licence
There is no licence, and it's always illegal. However, you may have a defence.
Our defence hangs on the very thinnest of pegs. It was added to the defences as the very catchy "the organisation and holding of permitted activities for which public liability insurance is held in relation to liabilities to third parties arising from or in connection with the organisation and holding of those activities".
https://www.legislation.gov.uk/uksi/2007/2606/regulation/3/made
This was then expanded on by some Joe Nobody in the Home Office to mean "the organisation and holding of airsoft skirmishing" and "The defence for airsoft skirmishing can apply to individual players because their purchase of realistic imitation firearms for this purpose is considered part of the “holding” of a skirmishing event"
https://www.gov.uk/government/publications/the-violent-crime-reduction-act-2006-commencement-no-3-order-2007-firearms-measures
A scheme that looks quite like the current UKARA one is described, but it's suggestive, not prescriptive. The defence in the (modified) statute is simply "to show that his conduct was for the purpose only of making the imitation firearm in question available for one or more of the purposes specified" (e.g. airsoft skirmishing).
tl;dr version - the defence actually relies on future intent, not past behaviour, although you need to adduce it rather than just assert it. So book another game day, paint or strip it,
be sensible with its use, and it's not going to be an issue for you.
Of course, if you're not actually an active airsoft skirmisher, none of this applies, but it's not like me saying "Gonnae no spray that" will actually
stop you from doing it.