How much to convert a loft +stairs?

[HeartOrHeadDecision]

Oh could somebody give me a hint at the price please? To build the stairs, convert the loft. Possibly add a bathroom. Add a Juliette balcony? Would be helpful to get a rough idea before buying a house.
We are in the South

@TeenagersAngst but the thinking is usually that oh we cannot afford a proper 4 bed let's convert the loft when we get hold of some cash and then it is a shock as actually a ready done 4 bed is probably same minus all the nerves.

This property will, however, rise in price regardless. It is a very sought after location.

@christmastreefarm it is as open as it gets. A joined kitchen/diner. No doors anywhere but to the loo.
Didn't think about that TBH. A good point

With a trussed roof you are basically going to need a new roof on top of the loft conversion price. I would estimate £120-140k easily for a finished result with a bathroom.

@HeartOrHeadDecision think carefully before you purchase this property, we made a mistake when having to make a similar decision.
We bought a 2 bed bungalow with a good size loft to do a conversion. Before buying it, we brought in an architect and he gave us a quote.
We then purchased the property, invested a lot of time and money into just doing up the downstairs, spent money on the architect and plans for upstairs to only find out that no builder on the planet would do the project for the money he quoted (this architect plans houses, gets builders to build them and then sells them so we trusted him with the quote, sadly).
We know have a property we overpaid for (it's in a sought after location for), spent a lot of money on doing up but won't be converting the loft as it just makes more sense to sell and buy bigger in the future.
If you could get a quote (from a few different builders) and then add that amount of money to what you're prepared to pay for this house, would that money afford you a 4 bed property?

*sought after location though