Two smaller sheds or a custom built lean-to might be a cheaper
proposition.
If you get the urge to build one yourself from scratch then google search
through uk.d-i-y - a few people have posted good descriptions about the
construction of their sheds. If you were to price up the materials for
framing, roofing, cladding with shiplap or featheredge, flooring, doors,
windows, etc, then you may find that you are not saving that much.

For the price quoted I'd be expecting cladding with shiplap rather than
(cheaper) featheredge.


Thanks for the useful info.