Best place for £200k cash for a year to 18 months

[Deangtv]

I appreciate it wouldn't be under the mattress and I assume the ISA route, but i'm selling my house and cashing out the equity in the hope of purchasing some land and heading down the self build route.
We will be renting for a year or so so i need to get my £200k working as hard as it can in the mean time whilst i sort the planning out.

What are people thoughts. Low risk please, not silly loan shark ideas gents