Guya,
The definition of lump sum is different under domestic US law from the definition under domestic UK law. This can be used to a taxpayer's advantage. I'd be happy to share the results of my research on this topic offline. You'd have to PM me...
SweetPeach,
It's nearly impossible to provide a conservative position on this topic due to the differing definitions. You might be well-considered to take professional advice in this case, otherwise you are taking a certain amount of risk without any one to back you up. Accountants have professional indemnity insurance which can protect you to a certain extent from the results of taking a less-than-conservative position in a grey area. Alternatively, you could consider using another source of funds.