Work permit for an American company doing business in the UK?

I am planning on moving to the UK with my family the beginning of the year.  It will be a projected six to eight month project.  My company sells machinery and I will be going as engineering support to the UK sales rep that lives in London.  The UK sales rep is self employed.  The question I have is what type of Visa do we need?  From what I could gather from the various web sites is that under six months I don't need a work permit.  Over six months I need a work permit which has to be applied for by a UK company.

Regards,
Daniel

P.S.  I really don't want to call the British Consulate in the US because they charge $2 per minute.  And that just bugs me.

I would need more detail on what you mean by 'engineering support'.  It may be that you could od this on a business visit, although a work permit will probably be necessary.  Also, how will the secondment be structured?  Where will you be paid from?

Vicky

I used the term engineer in the British context.  Basically I would be doing sales and service work on the machinery that we manufacture.  I would also be evaluating the UK and mainland European market for expansion.  We have the one rep in the UK and are looking into adding more.
I don't understand the term "secondment".  I will be paid from the US.
Daniel

If you are doing engineering work on a proprietary piece of machinery for your company then it is likely a visit visa would be fine.  I would like a really detailed description of your role to make sure as it is an extremely grey area.  You can PM me if you like.

'Doing sales work' however is different.  Sales to whom?

Vicky