In reply to Humphrey Jungle:
I am a chartered surveyor and am doing Homebuyer Surveys and Building Surveys every day.
A Valuation Survey is just a valuation, the surveyor will not do an in depth inspection - it is just cursory, and it should never be relied upon if you are concerned about the condition of the property.
A Homebuyer Survey is a concise report and the inspection should be thorough, and cover much the same ground as a full Building Survey (thats what I do anyway). The difference lies in the detail reported. The HBS will not report on minor defects, unless the cumulative total is sufficient to affect the value. Significant items will be reported. The definition of "significant" is where in the surveyor's opinion the defect is serious enough to affect the value of the property. The surveyor will also report on urgent or developing repairs which if not dealt with will result in significant damage or problems. It is ideal for small properties, particularly post WW2 construction, and for flats *. It will include a Valuation and a re-instatement valuation for insurance purposes.
A Full Building Survey is a bespoke survey, and will report in a lot more detail, and cover any particular matters of concern to the buyer. It is ideal for large or period property, or propertiies of non conventional construction. It will not nessessarily include a valuation, and is often undertaken by Building Surveyors who may not be Valuers.
* I see you are talking about a Tenement. It is very difficult to do a Full Buiding Survey on a flat in isolation from the other flats in the building. A lot will depend on the Lease Terms and your share of maintenance liability.
If you are going for a Homebuyer Survey it is absolutely vital that you talk directly with the surveyor who will be doing it to discuss with him/her your particular concerns, and just what they will be doing. If you are unclear about anything in their report discuss it with them and ask them to expand. This is the advantage of using an individual Chartered Surveyor who has been recommended to you rather than one of the faceless large multiple firms where you generally have no control over which surveyor does it.