Public supplier prices are usually starting points. They may exclude foundations, transport constraints, crane or lifting needs, utility connections, wastewater, fire and building control requirements, professional fees, upgrades, and VAT treatment.
For early budgeting, separate the unit price from site-specific works. A compact unit that looks affordable online can move into a different budget band if access is tight, drainage is complex, or the supplier needs bespoke compliance work.
Finance also needs care. Some suppliers publish mortgageable or finance-ready claims for specific systems, while others are cash, credit union, or private finance routes. Treat those claims as supplier-specific until a lender or broker confirms the product and site.
The quote flow captures budget range and funding route so we can separate simple comparison leads from cases that may need finance, site survey, or compliance advice.
Cost bands to sanity-check
For a first pass, separate the project into three buckets:
| Cost bucket | What to include |
|---|---|
| Modular unit | Shell or finished unit, bathroom, kitchen, insulation, heating, windows, doors, internal finishes, and manufacturer warranty. |
| Site works | Foundations, access preparation, lifting, drainage, water, electricity, wastewater, broadband route, paths, landscaping, and making good. |
| Professional and compliance costs | Planning advice, drawings, building control, fire safety details, certification, insurance checks, legal/title questions, and finance paperwork. |
The lowest online unit price can be useful for comparison, but it is rarely the final installed cost. A small urban garden with tight access can cost more to install than a larger rural garden with a simple delivery route. A rural site can also become more expensive if wastewater, road access or utility distance is difficult.
Quote questions that reduce surprises
Ask every supplier to confirm what is included, what is provisional, and what is excluded. A useful quote should say whether it includes VAT, transport, craneage, foundations, services, connection works, certification, warranty, snagging, and aftercare.
If a supplier gives a fast headline price, ask what site information they assumed. The biggest mistakes happen when a buyer compares a bare unit price against another supplier's installed price.
Finance and affordability
Mortgage, credit union, personal loan, savings, family funding, and specialist finance routes all have different risk profiles. Lenders may care about whether the unit is permanent, insurable, certified, saleable, and legally connected to the property title. Do not assume a supplier's finance wording applies to your site until a lender or broker confirms it in writing.
Use county pages and the supplier directory to build a shortlist, then request comparable quotes with the same project brief.