responsive form modifications

I need this form coding so that it only sends the fields that are completed [login to view URL] for example all the fields on the left are required so error checking needs to be present - the same that is used if possible. Its the fields on the right mainly because if only one car is selected it currently sends the other two below it with blank entries as shown below. The email must be plain text because most of the time the client views the email on his phone. So if the user only wants one car it only sends that and not the other two and if they want two cars it send them details leaving the third off. The website is responsive so it must stay within the design because it is working perfect. The current code is very basic so feel free to recode if needed. Car 1: Stretched Beauford 1 Time at house for: 2 o'clock Pick Up Number: 1 Trips From House: 1 Guests To Be Taken To Church: Mum Address To Be Picked Up From: Stratford Postcode: M32 oua Car 2: Time at house for: Pick Up Number: Trips From House: Guests To Be Taken To Church: Address To Be Picked Up From: Postcode: Car 3: Time at house for: Pick Up Number: Trips From House: Guests To Be Taken To Church: Address To Be Picked Up From: Postcode: