Have you asked the current owners what speeds they actually get on their broadband? it may be better or worse than you think.
If you know the phone number of the house - which you can get from the BT Phonebook if you know the surname and they're not ex-directory - then enter it at
https://www.broadbandchecker.btwholesale.com and it will show you the *actual* speeds achieved recently under the heading "Observed Speeds".
Here's mine, which might be relevant since I get very similar predicted speeds to yours:
VDSL Range A (Clean) 35.5 24.9 6 4.3 22 Available Available --
VDSL Range B (Impacted) 34.5 21.2 6 3.6 17.7 Available Available
Observed Speeds VDSL
Max Observed Downstream Speed 30.81
Max Observed Upstream Speed 3.84
Observed Date 2020-12-23
You'll only see this if the current occupiers have an FTTC broadband service of course. ADSL figures aren't useful, and if they take ADSL from an LLU provider (e.g. Talktalk) then it won't even recognise the phone number.
For me, moving from a house where I got 70/17 was a very noticeable step down, especially for uploads. But it was really the house we wanted.
In the end, I got FTTPoD installed: the cost was considerable (but still less than stamp duty) and I got a business voucher towards it. I think I was lucky to get in early in 2018: based on reports from forum users, the typical cost of FTTPoD appears to have increased substantially since then.
I kept the FTTC line to keep business and home usage separate for accounting purposes - and it also means I have a backup, although the FTTP has not failed once, whilst FTTC has several times.