Superfast broadband is rate dependent like ADSL but it the distance to the 'fibre' cabinet that is the overriding factor regarding how close to the maximum rate the product you buy has ( 40Mb, 55Mb,80Mb,) if the line is only capable of 50Mb, then IMHO'buying' 80Mb Superfast 2 would be pointless, as you would never achieve it, but if you are quite close to the fibre cab , then 80Mb ( if that's what you purchase) isn't unusual
Enter you phone number at a checker site like this one, it will show your predicted speed , on a clean line and an impacted line
if you post the results obscure your phone number
Got told 50 mps is normal and to be expected. What can I expect realistically
It can't be worse than the 7mps I currently get with my current isp
As @iniltous has said, there is no such thing as 'normal', every line is unique but the checker will give a good estimate. However, until connected actual speed will not be known accurately. The checker figure tends to err on the cautious side with the estimated speed generally.
Then you will get somewhere between 80M and 63.3M, probably closer to the higher figure. If you are happy with 55M, just order Superfast1 and save a bit of money.