Hi, I am wobblypig's husband and she has just passed the keyboard to me as I am a patent attorney - just set up my own business after many years employed in intellectul property. You can do a certain amount of searching using patent publication databases such as :
Don't get too hung up on searching though as it generally won't give you anything definitive. Speak to a patent attorney (not a lawyer) about the idea and get their advice on whether the idea is patentable. The Intellectual Property Office (formerly Patent Office) will conduct a search as part of the patenting process.
Most patent firms should provide an initial consultation free of charge (make sure you check first). I certainly do. I'd be happy to chat to you about it. Although my business is new I do advise James Caan on his Dragon's Den investments so I am pretty experienced. Let me know and i'll email you my details.
One more thing - you are right to be cagey initially as the most important thing about the patent process is that the invention must be new (not disclosed publically) before the date you have applied for protection - any formal discussions with patent attorneys though is bound by client confidentiality.
No problem at all. For preparing and filing a UK patent application I would charge around £1000 to £1500 (+VAT). Because I have little overheads I can charge quite low. Most other Firms I am aware of are more likely to charge £2000+. That would be it for one year, then there would be more charges to continue but by then you should have an idea of whether or not the idea is going to make you money. This is for a patent - it may be the case that the idea is best protected through a registered design(in which case the cost is more like £350) or trade mark (around £450). It all depends what the idea is.