Recommendations for wireless router?

[Engram]

Which wireless router would you guys recommend, given these constraints:

• Doesn't need a built-in modem (I'll use my Openreach Fibre modem)
• Must support 802.11ac or better
  
• Must support OpenVPN server
• Ideally would support guest Wi-Fi
• Ideally would cost < £100

There seem to be a crazy number of routers available now, and it's really hard to figure out which ones are actually any good.