No problem at all.
Here's what the FM -SE of UKBA states:-
...paragraph 2A of Appendix FM-SE specifies that P60(s) for the relevant period(s) of employment (if issued) and a signed contract(s) of employment may also be submitted in respect of paid employment in the UK. If they are not submitted, the decision-maker may grant the application if otherwise satisfied that the requirements of Appendix FM-SE relating to that employment are met, or they may ask for the documents to be submitted in accordance with paragraph D of the Appendix.....