For starting out in the UK I'd recommend a simple sturdy gun like a Beuchat 75cm. Cheap strong reliable, the original brick sh*thouse. Then if you managed to catch a few fish I'd move on to an omer XXV Gold. Only when you are good with that would I recommend something more fancy, even a mamba 90 air gun.
However, I am sure you will ignore this advice as it is much too sensible and frankly boring. Most newbee's buy a fancy gun but then most of them catch very little and give up.
If you were a learner driver I'm sure you'd like to own a Ferrari but would it be of any use to you? It would be way more than you would need or could handle. Better to but a Fiesta, get some experience and then try the Ferrari.
Bet you ignore this anyway

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Dave