Sales projections for retail business plan

A quick fix is to try the Businessesforsale site http://uk.businessesforsale.com/uk/1293601-1/browse.aspx There's a Deli on there in Bedfordshire that does £2500 a week in sales with a 39% profit margin, so that's a starting point I've cut and pasted the details below. Marcus Bedfordshire, United Kingdom Asking price: £29,950 Sales revenue: £113,295 IMMACULATELY PRESENTED AIR CONDITIONED DELI-STYLE SPECIALIST FOOD OUTLET. Space and potential for small coffee shop customer seating area at the rear. Fully equipped, well known and long established going concern. Five year lease renewable in June 2004 - current rent only £6,500 per annum (new lease may be available on change of ownership, if required). Current gross weekly sales average c£2,500 @ approximately 39% profit margin (accounts on file at our office). The business offers a tempting range of traditional farmhouse cheeses, frozen ready cooked meals for all occasions, Italian breads, deli foods, gourmet packaged goods, pickles, pastries, jams, mustards etc, plus a thriving and expanding take-away section of jacket potatoes, soup, filled rolls and sandwiches (all made to order). Employees: The business is currently run by our client on a full-time basis with the assistance of three part-time ladies plus one Saturday girl. The current annual wage bill is c£15,000 – this could be reduced considerably if the business was acquired by a partnership intending to both work full-time in the business. Trading hours: Monday 9.00am – 2.00pm, Tuesday – Friday 9.00am – 5.30pm, Saturday 8.00am – 3.30pm Property Leasehold Lease terms: We are informed by our clients that the property is currently subject to a lease term of five years renewable in June 2004, when a further (minimum) five year term will be available. The current annual rental is £6,500 – there is little reason for this figure to be increased by any substantial amount when the lease is renewed. Alternatively, we could approach the landlord and seek a brand new lease, on terms to be agreed, to commence on change of ownership. Location The business is situated within a thriving edge of town centre shopping area, particularly well known for specialist retailers, in this North Bedfordshire town, close to the embankment of The River Ouse. Other retailers include a fishmonger, butcher, fresh pasta shop, Post Office, small supermarket (multiple owned), newsagent, Chinese take away plus numerous other complimentary concerns. Customers include local residents, local office professionals, who use the area for lunchtime shopping, passing motorists plus shoppers from the surrounding area. A particular benefit is that there is ample free car parking in the immediate area. Editor - Startups.co.uk
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Editor-in-chief - Startups.co.uk

Thanks. Is this a recognised way of estimating turnover for business plans - have any other people used this method ?