In 1991 the cold war had just ended. The UK was still fielding jets built in the 50s. It has Buccaneers, Phantoms, Jaguars, Tornados etc. Today the RAF is quite literally bare bones. If you've read various defence journals over the last decade you'll have seen the Harrier force cut to free up cash for Tornado. Tornado scrapped for a Eurofighter upgrade. F35 numbers slashed etc. Typhoons were being stripped for parts to keep others flying etc. Tranche 1 is to be scrapped after only 20 years of service and not upgraded. 20 years is nothing for a jet that has a considerable service life. The UK quite literally has no jets to give away. It's not like you can just give away modern, complicated hardware anyway as it needs a complete support and logistics service. It's not as simple as sending over some tanks made in the 60s where all you need is some ammunition and an instruction manual that hasn't changed in principle since the 30s.