Any estate agents on here ( or people who are involved in property ) ? ? ?

We have seen a house that we like the look of, needs work but the location is great and the plot size is outstanding ( just under 1/2 of a acre ) its down a country lane and well out of the way,

now they are asking for sealed bids in the region of £400 K , I am thinking with the house extended ( its now 3 bed ) to maybe 5 or 6 bed with a double ( or triple ) garage the house would be worth maybe 650 K ( which having searched looks reasonable ) who would have thought a boy from barry living in a 650 K house

anyways, what is the norm when doing these sealed bids, do you bid upto the in the region of price ? ? ? go much over it ? ? ? chance it with a low ball figure ? ??