"David W.E. Roberts" wrote
| The plot is not particularly large - the floor area is roughly the
| same as the ground floor of our current 4/5 bedroom house and the
| garden is smaller.
| The small cul-de-sac has nothing but bungalows on it (all the same
| design) - so planning for a new 2 storey property may be an issue.

Yes.

| The bungalow is 1930's - which means that it has a huge high loft
| with real wood beams and no cheap crap cross braced supports as
| found in most modern builds. So there is an obvious potential to
| make more of this loft area. The downside is the 2" * 4" joists.
| Other properties in this street have already had loft conversions
| (but no dormers).

That sounds /very/ promising, but dormer would add some very useful
headroom. One advantage of loft-converting a bungalow is you don't have the
fire safety regulations which come into force when you take a property into
three storeys.

| There are 4 downstairs rooms (excluding kitchen/bathroom) which really
| makes it a 2 bedroom bungalow, although it is currently used as a 3
| bedoom bungalow with a 16' lounge/diner. This would do us fine as a
| 'mature couple' but unfortunately we are currently infested with
| adult super-rugrats (in urban environments they can grow to 6' 2"
| or more) and need a minimum of 3 bedrooms until the poisoned bait
| (my cooking) or the lure of the great blue yonder clears some space
| for us.
| So I am looking for ways in which a modest outlay (£25k or less)
| can expand the accomodation to cope with occasional peaks (Lord help
| us all if they ever breed) and still leave us with some cash to spend
| on ourselves.

A lot will depend on the site and this might not make you popular with your
neighbours, but £25k will get you an ex campsite static caravan. A lot less
will get you an ex building site static caravan. Planning permission is not
normally needed for a caravan provided it is not used as a self-contained
dwelling (ie it's part of your own household). It might be a blunt reminder
to the super-rugrats that you're not expecting them to be a permanent
fixture. Further encouragement to fly the nest could be provided by giving
them only a 5A electricity supply in the depths of winter. Of course, it
wouldn't add value to the house like a loft conversion, but it also wouldn't
permanently rob you of garden like a ground level extension.

Owain