Compared to the top die,the RTX4070 is actually the real equivalent of your GTX1660TI. The RTX4060TI is really a 50 class die.
I would wait for the RTX5000 series,or an RTX4000 Super refresh. If you can't wait now,I would just get an RTX3060 12GB for £279(it might even drop further in price):
The RTX4060TI 16GB is going to be £200 more. Plus like the RX7600,it is underprovisioned in terms of cache(both have 32MB),so this is why they both have issues at higher resolutions and with some games. Plus unless you have a PCI-E 4.0 system,expect a few extra percent performance to be lost.
I would not be paying much over £250 for an 8GB dGPU in 2023.