To throw my experience into the equation. Whilst Dave clearly has some good points, I would raise some concerns.
Firstly, in appointing an agreed surveyor for such a complex project. Basement conversions manifest in some form of damage some 80% + of the time and having two surveyors working towards a resolve will clearly outweigh the experience and knowledge of one (twice as much funnily).
Secondly, I would be concerned about obtaining a fixed fee in this instance due to as mentioned the complexity by nature of a basement conversion. There will be a range of professionals that may be called upon including structural engineers and designers, this all requires a level of diligence and indeed enough time to co-ordinate and manage.
Having one surveyor to rely on in my opionion is too risky as they indeed become, judge jury and executioner. If there is an air of difference between the two surveyors you also have recourse from a third surveyor, who are very well versed and experienced practitioners.
Also, to put a figure on a adjoining owners fees without first at least determining the very nature of the proposed plans and works is nieve. If said surveyor spends 35 hours including several site inspections at an agreed £800 this will amount to £9 odd an hour...the chances of the agreed surveyor cutting corners or deploying junior staff with no tangible experience is highly likely, all at the detriment to the neighbours in question, very much against the spirit of the Act.
To say there is no technical involvement is also a cause for concern. Party wall surveyors are required to utilise their specialist construction knowledge and understanding of the Act to resolve disputes. Building technology, modern methods of construction and indeed renovation of period properties certainly require a technical level of building and construction expertise, coupled with a requirement of understanding the the relevant law on par with legal practitioners.
It is for that reason that I for one would definently not engage a bargain budget party wall practitioner to oversee professional and legal inactment of legislation over ones most valuable asset.
My experience; 20 years building and construction, 12 years of part time construction and building surveying formal education including land and contract law, and a first class honours in RICS accredited Building Surveying degree (who so happened to undertake their major project in Party Wall).
I have seen too many cowboys, too many fancy websites, too much inexperience in the field of Party Wall surveying.... rather than asking about liability insurance (virtually impossible that this would ever come into play unless you was hell bent on causing carnage!), I would be more focused on ones construction experience, party wall knowledge, and previous appointments.
I can recite the Party Wall etc. Act 1996, and I have been involved with minor through to major works both in a hands on and managerial capacity.
Go recommended, go local. If you are based in and around North London, I would be happy to offer free impartial advice. I also currently assist several individuals on and pro bono basis across the UK.
I also specialise in providing non profit and social housing providers with a personalised service, which I am very proud of. Contact me by email at
Info@tksurveyinggroup.co.uk or through our Web portal at
http://www.tksurveyinggroup.co.uk if you have any questions.