I just had a look on Samsung's website and they didn't give any options to proceed past trouble shooting for the repair without the IMEI of your phone (please do not post it here that poses security concerns)
If I was to make an educated guess I would say it could range anywhere from £200 - £350 for the repair
And for a now 4 year old phone Its just not worth doing you may as well either trade it in for a newer model, use it untill it fails or take the money you would have spent on the repair and buy a new phone
I'd recommend the s23, you can get that for around £500 brand new if you look in the right places
Or
Get the A55 (£450), the A33 (£350), the A54(£250)
I'd personally recommend the S23 because it's a flagship or the A54 because it's just a solid phone
I hope this helps