I don’t think anyone is going to give you a hard time on here for buying a Carerra. Voodoo and Boardman are often touted as being great VFM bikes.
As others have said be mindful of what the ceiling is on that bike, 1 1/8th straight steerer and QR is going to limit you to lower end forks (as you note). You might be able to get a tapered fork in there but that’s still another £25 min on a new headset. Going tapered probably wouldn’t be compatible with 9mm QR either (would probably need a new front wheel – another ~£100).
You say spending £250-£300 on upgrading but are you going to get:
– forks
– cranks
– tyres
– bars
– dropper
for less than £300? surely if buying new you’re looking at £400 or £500 at least. The second hand bike market is pretty buoyant right now, are you better off looking at what you could sell the current bike for and buying something slightly higher spec instead?
Something like this, Sonder Transmitter. Would probably want to splash another £130 on a dropper on top of that.
I’m not saying the upgrades are pointless and the bike is somehow flawed. I’m sure you’ll have fun on the bike (upgraded or not). Just that with what you’re proposing you’ll potentially end up walking into unexpected costs and for similar money you could end up with something better spec/more future proof.