How long you are out
Typical move-out to move-back-in is 12-18 months: 1 month to clear the house, 12 weeks demolition and foundations, 36 weeks build and fit-out, snag and handover. Add planning buffer at the front (3-6 months) if you cannot move in with finance signed but planning still in determination.
Regional median 3-bed rents
ONS Private rent and house prices bulletin (May 2026 release) puts median 3-bed private rents at roughly: London £2,950/mo, South East £2,100/mo, Surrey £2,350, Herts £2,050, Bucks £2,000, Kent £1,900, Essex £1,850, Edinburgh £1,750, Cardiff £1,500, Manchester £1,450, Birmingham £1,400, Yorkshire £1,350[ONS rents].
Storage
Self-storage at £200-£600/mo for a 3-bed contents depending on unit size and region. Pod storage (delivered to plot post-build) similar. Removals at each end £800-£1,800. The total ancillary cost block typically lands £3k-£10k.
Reclaim routes
Buildings insurance rarely covers temp accom for voluntary works; only insured peril (fire, flood) triggers alternative-accommodation cover. Self-build mortgages do not advance funds against rent. Treat temp accom as a budgeted cash line, not a recoverable item.