THROUGHOUT Britain, those poets of property who have turned a dump into a ''handyman's dream'' or transformed the cramped cottage into ''snug and cosy'' have been silenced. No more will the prospective purchaser be proffered purple prose by the Shakespeares of the semi-detached, the Byrons of brick-veneer. New legislation in Britain has halted the time-honoured practice of waxing lyrical about real estate at the expense, sometimes, of the facts. And the property industry is having a bit of trouble coming to terms with the new ground rules. The Property Misdescription Act, which came into effect this month, has claimed among its first victims a castle in Scotland. The original glossy 10-page brochure for Dunselma Castle near Argyle described it as ''a fairytale Victorian Castle built in an elevated situation commanding breathtaking views in all directions''. That was until the finer points of the act were made known to the agents selling the castle. A page of corrections added to the brochure changed the description to the austere: ''Victorian castle in terraced grounds with woodland.'' But the agents appear to have over-reacted somewhat to their errors. Whereas the original brochure described the Cowal Peninsula, where the castle stands, as ''one of the best kept secrets in Scotland'' and ''an area of outstanding scenic beauty'', the corrections says: ''While we believe the Cowal Peninsula to be an area of outstanding scenic beauty, we are unable to confirm that it ranks top among Scotland's attractions.'' And some changes verge on the paranoid. While the brochure says there are ''uninterrupted views'', the correction states the views are in fact ''interrupted by occasional trees''. Another property to suffer the same fate is a thatched cottage in Buckinghamshire once lived in by children's writer Enid Blyton, creator of Noddy and Big Ears. Before the new act, it would have been tailor-made for a description along the lines of ''Dream home immortalised in children's literature'' or the ''Fairytale thatched cottage where Noddy and Big Ears entered the world''. Instead, it has become a plain old ''former inn with an interesting history attached to it'', which does not quite have the same ring. The words ''delightful'' and ''attractive'' are, according to the National Association of Estate Agents, where difficulties arise. Who says it is attractive? And while it may be delightful to one person, another may not agree.