The only reason Evoques command high prices is status. I reckon that 125k miles wipes out that status. £20k is far too much and could lead to a lot of trouble. The first thing it needs is a new timing belt, tensioner and waterpump. The next thing will be a new DMF and clutch (assuming it's manual). As well as that a new EGR, new DPF, new turbo. About £6k of grief. So if you can't chip it down to £15k, leave it alone.