1.   I wrote back to them immediately, thanking them for their kind invitation.

2.   Mr Casey regrets that he will have to Decline your kind invitation owing to a prior engagement.

3.   Ms Jarvis is unable to accept your kind invitation.

4.   No offer of financial help, no kind invitations to join them in club activities were forthcoming from Charles.

5.   Mrs Armstrong regrets that she cannot accept your kind invitation.

6.   Thank you for your kind invitation.