Aerocool Cylon 700W 80 Plus Certified Power Supply Unit £32.40 - Sold by Scan on Amazon

Click on the other sellers link and select Scan.

• Up To 85%+ Efficiency - 80Plus 230V EU Standard Certified for high efficiency performance
• Silent 12 cm fan with optimised thermal fan speed control - Fan runs at startup speed (less than 800RPM) before reaching 60% load at 25°C ambient temperatures
• Soft, black, flat cables allow for more convenient cable management and easier installation
• Compatible with all Intel form factors up to ATX12V Ver.2.4

*probably won't blow your PC up, but I wouldn't bank on it delivering a continuous 700w to power an RTX3070.

Leaving aside comments about how good this PSU is compared to something twice the price, I think this is a good price.