So I bought BTC at £9000, made a nice amount. Is it a good idea to now sell this and move that money into alt coins? or should I sell half BTC and buy back in after alt season is finished?
What do you think?
I would sell half of my BTC for USD/USDT and wouldn't touch it for now, with the other half you can buy 50% some quality altcoins which you believe in and keep the other 50% in BTC and see what happens and take your chance as bullrun most probably isn't even close to over yet, but you should always take some profits while you can so that you don't get out of your trade/investment with a loss at least.
If you want to buy altcoins, be fully diversified into 4-5 different projects with different use cases, for example do not buy/invest in 5 DeFi projects and think you're safe now, since usually every new hype whether it's DeFi, NFT or whatever else has to correct at some point and you don't want to be all in one of them when/if that happens.