Introduction / sales commission paid 2 years after employment

Scenario:

In 2009 Consultant A, a UK resident and tax payer, working on a freelance basis under an "umbrella company" which paid PAYE out of contract income, signs a contract to introduce Company B to Company C.  If the result of said introduction produces any revenue for Company B then Consultant A is paid 2.5% commission from the year 1 revenues arising and 1.25% in year 2.  Company B is based in Bulgaria and will pay the commission in Euros (being the currency of contract with Company C).  

In 2011 Company C finally enters into a commercial relationship with Company B thus triggering Consultant A's entitlement to payments out of 20,000 Euros per month of revenue.  These are to be paid as Company B receives revenue from Company C.  Consultant A elects to take this payment quarterly to minimise bank charges on payments on relatively small amounts.

Since 2010 Consultant A resigned their freelancing work under the Umbrella Company and became a full time employee of a different unrelated business.  Special terms were negotiated with the new employer to allow continuation of the terms of the contract with Company B - normal employment terms forbid any commercial relationships with other companies.  Ex Consultant A is a higher rate tax payer, any additional income is likely to push total taxable earnings above £100,000 per annum.

Question:

Ex Consultant A is now ready to receive commission payments and must raise invoices to trigger payments which will be quarterly until end of 2013.  The question is how should ex consultant A treat the income for Self Assessment purposes and also for National Insurance?

Given the tax situation it might seem efficient to put the income into a pension policy, however as ex Consultant A has credit card debts of £47,000 their preference is to repay the debts as much as possible.

Many thanks for any advice!