Honestly, Airsoft is an expensive sport, especially when things inevitably break or go wrong. Being as kind as possible, I would suggest that if you cant afford the gear, you probably cant afford the £25/£30 per person skirmish fee and the £10 bottle each on BBs per session.
There is no need for a secondary especially as you're asking for free stuff. Many people don't run a secondary. Secondaries also usually mean a pistol, which have additional costs such as gas, magazines (Which are a minimum of around £25 each) and holster. Secondaries don't perform as well as your primary. You don't need it when you are new and on a budget .
The other issue is that although some might not have a problem, I would not want to give away a RIF to a new or casual player. Only a two toned IF.
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However if you are determined to start on very little money and you don't want to go for the rental options.
Buy two of these AK's. They are the cheapest rifles I would even bother with. They have quite good internals for the money which are unlikely to go boom the first time you fire them.
https://gunfire.com/en/products/jg-0512mg-replica-1152194697.html
And the service to spray paint them so they are IFs and can be legally imported for new players such as yourselves without the need for a provable defence.
https://gunfire.com/en/products/painting-service-servico-de-pintura-make-the-airsoft-gun-meet-your-local-law-requirements-1152211293.html
As well as this service for both rifles to downgrade them to UK levels of 1 Joule.
https://gunfire.com/en/products/aeg-replica-downgrade-1152197807.html
You would also need a battery and charger.
If you're not a fan of AK's or importing then try two of these .
https://www.bespokeairsoft.co.uk/airsoft-gun/cyma-cm515-m4-long-ris-aeg-sports-line-black-cm515
Or
https://www.patrolbase.co.uk/cyma-cm-513-m4-ris-suppressed?pv=2611
https://www.patrolbase.co.uk/cyma-cm-507-ar-15?pv=8569
Already UK spec and you can pick the colour (Red or Blue) for the RIF to be painted account for your lack of defense. Is already UK spec and also comes with battery and charger. Its a bit more expensive then the AK's and Cyma make a better AK then they do an M4. But it is convenient.
I do have my UKARA number so was hoping to get something realistic for me.