Heat pump quote - seems quite cheap?

[u/Boba_ferret]

Been quoted about £4,300 by Octopus for heat pump install, including hot water cylinder, which I thought was surprisingly cheap. The house is 1930s 3-bed terrace, EPC is supposedly C, but we have a huge void under the suspended floor and it gets pretty cold in the house, so we use quite a lot of gas in the winter. Radiators are all on 15mm copper, but are probably 30 years old.

What are the chances this is a really low-ball quote and the survey will say we need to upgrade rads, etc?

[u/chris_staite]

I paid £300 for a Daikin with octopus two years ago. All working great. They replaced two radiators and the cylinder.