Tier 2 Change of employer NOTICE URGENT...GURUS PLEASE HELP

[NMohammed]

Hi,

I am working for company A on TIER 2,but recently I got a conditional offer from company B,so i accepted it and switched my visa to company B sponsorship and recevied my new BRP card.
But i am still working for company A,because the start date on company B cos is 1st Sept so i think i can legally work of company A till 31st August.(correct me if i am wrong)

However as i have to complete 1 week notice period at company A i am thinking to resign by the end of this week so that i can complete 1 week notice(i.e next week).

But the problem is that although i got my visa I have not recevied my unconditional offer yet.
My new employer is saying that start date is definetly 1st Sep but it will take them some time to generate the contract, so i might receive it (pdf copy) by friday after noon or next week.

If i receive it on friday,that's good but the problem is, on friday ,we have business continuty test at company A so i will be working from home so i can not hand in my resignation in person,i have to send an email ,can i do that?

if i do not receive the contract this week what options do i have?
can i extend my start date? or should i resign this week itself,irrespective of receving the contract as i got the new visa already?

Please help me out.

Thanks and regards,

[NMohammed]

Please advice me guys.

[NMohammed]

Guys please help me out...Manci could you please advice me?