It's not worth it. You'd literally earn less in bitcoin (pennies per day) than it would cost you in electricity. You're about 18 months too late where a small investment might earn a few bitcoins. Even if you were to invest tens of thousands of dollars, you'd still be very lucky to break even after a year.
It's literally become a money-making endeavor for very, very few people except for the massive mining operations. There are many of us home miners who have been doing this for a relatively long time and some of us have done pretty well by making well-timed investments in mining equipment. But even for us, our days are numbered. By the end of summer, a lot of us will be shutting our gear down because we won't be able to earn enough from mining to cover our electricity costs.
I'd disagree, you can spend 4000£ (or whatever in dollars) into some wise choices of hardware and make your money back and more still. You're making the world sound a lot more bleak than it actually is...
You're in denial. Do the math.
What can you buy for $6000 today and start hashing tomorrow? So you maybe buy 3 AntMiner S2s for 3THs. That earns you about 0.15 BTC per day or $90 (less electricity costs). You can maybe double that before you've maxed out the electricity in your home. And then in 8 hours from now, your income drops by 15% when the difficulty adjusts. Then 11 days from now it drops another 10-20%.
Yes, home mining is indeed on it's last leg.
I know the reality of the situation, I've been doing this since the first days of the AM USB Block Erupters (and a few months before with a several GPUs). I doubled my hashrate probably nearly every month and currently hash with ~7.5THs. I've tripped my main breaker three times! And my house is extremely hot (well over 80f during the day) despite adding auxiliary A/C to my central A/C. My electric bill last month was over $1300. And I'm not running any inefficient gear. I long ago retired my BFL Singles and ASICMiner Blades. I have about 2 more months of mining before it no longer makes financial sense to run my gear. And to tell the truth, I'm looking forward to that day!
Oh but super efficient ASICs are coming soon! Sure, but by the time they finally arrive, a new massive investment will only extend my mining by another 3 months before it's over again. And I will surely never recoup that investment.