Hi all,   We're out of space... wife and I both now work from home and using kids bedrooms as offices is not working. I'm getting kicked out into the proposed garden office....   So, we're tight on space (in the back garden), time and money - I've ruled out:     brick & block due to thick walls (small back garden), cost (cant afford a bricky) and larger slab/foundations     timber due to time (and potentially cost) so we're looking at a self build SIP offic