The official instructions from UCAS specifically say,
“You must enter all your qualifications – whether you have the result (even any that were ungraded) or you’re still awaiting exams and results.”
https://www.ucas.com/ucas/undergraduate/apply-and-track/filling-your-application
And you have to sign this declaration:
http://help.ucas.com/contract12/index.html
which among other things says:
“If we, or a university or college, have any reason to believe that you or your referee have:
left out any information, including any qualifications you have completed, qualifications with an unsuccessful grade or qualifications for which you are still awaiting results,
given false or misleading information,
supplied a personal statement, or parts of a personal statement, that you have not written yourself,
we may take any necessary steps to check with you and other parties whether it is accurate or complete.
We have the right to cancel your application without giving you your application fee back, if we determine or (having carried out any necessary checks) or have reasonable belief that your application contains false information or you have not written your personal statement yourself.
If you have any reason to believe that information we have about you is not accurate or complete, you must tell us.”
It seems unlikely that they will drop this requirement in an e-mail to you.