It's a tricky one dude, unfortunately if you want a good router that price range is more entry level than mid-range. If that is your limit I would go for the
Asus AC57u for £55, it is going to be better than what you have got now in every regard and will be a solid average router. If you want a "mid-range" router then I can highly recommend the
AC68u, I have got it myself and is the bees knees. It is £140 but the excellent news for you is that you can buy a twin pack for £180 which is an absolute bargain. If you are thinking about future proofing with regards to wan to lan throughput and mesh wifi going forwards the twin pack would be the way to go. The AC68u supports mesh wifi and the 57u doesn't. Both routers are rated around 750mbits for wan to lan throughput.
Getting the twin pack is the way to go full stop because in terms of price they work out at £90 each which is a bargain. Mesh wifi isn't a necessity at the moment but it is definitely the way forward and if you can get such a great router now with mesh wifi as well you are laughing. I bought my routers separately so I have the ac68u serving as my main proper router and then I have an ac53u downstairs which is in access point mode (yup, a great feature from Asus) purely for wifi. There are lots of cables running around the house to each room so the router downstairs has a gigabit link to the ac68u and even though I am not using mesh wifi (the ac53u doesn't support it), every single one of my devices can get full speed over wifi anywhere in the house or outside in the garden. Normally this might be a cheaper option, especially if you were looking at multiple routers and wifi coverage, but even if you looked at two average non-mesh wifi routers like I suggested first you are still looking at £140 and depending on how big your house is I would rather just have one ac68u. The way I see it is that you have got 3 options:
1) Buy an entry level ac57u for £55
2) Buy a very very good ac68u for £140 which is excellent and will last yonks
3) Do a perfect job from the outset and what is also more cost effective and buy an ac68u twin pack and get mesh wifi up and running.
I'll warn you now, whatever you do don't go into a shop like Currys or Asda and buy whatever cheap ass crap they buy in bulk and say it is on offer. Routers are deceiving, you don't think you use them because you don't play with them like your pc or tv but they are in constant use 24/7 and arguably one of the most important items in your house. I know if my router died I would be lost until Amazon delivered the new one. My pearl of wisdom for the day is that a good router is worth its weight in gold and you pay for what you get.