If the bungalow is one of a scheme of identical/similar bungalows
have a walk round and see if any neighbours have loft conversions; if
several do then it's a good indication that conversion is possible
and economically viable. If you're brave you could even knock on
their door and ask them what it cost and which builder they used (and
look where they put the stairs). If no-one else has done a loft
conversion you might ask yourself why.

People often forget that bungalows have foundations intended for
single storey houses and conversion to a two storey might mean
improving the foundations. Costly and disruptive.

All very tentative at the moment - weighing up potential and future
costs in buying a detached 2 bedroom bungalow compared to buying a 3
bedroom semi.

Remember you might lose one of those 2 ground floor bedrooms when you
put the staircase in. But a det bung probably has more ground floor
extension potential than a semi, and with an ageing population ground
floor accessible bedrooms might be in more demand in future.

All sound advice. Also remember that you may well have difficulty obtaining
planning approval. At the very least you need to gto and talk to the
planners about what is, or more importantly is not, likely to be acceptable
to them.