Booked Connecting Flights - Time of First has changed

[nedite8864]

We booked connecting flights...

• Uk Manchester - Heathrow.
  
• Heathrow - Baltimore
  

We just got emailed and have been told they have changed the time of the first flight.. leaving us just 60min's for the connection.

So questions...

1. is 60 minutes going to be anywhere near enough time? my gut feel is that it won't be as the second flight will want us onboard well in advance of departure.
   
2. Do we need to go though custom's between the connections? or is it just a matter of getting off one flight and making our way to the next? I know it can take a while to get off a flight etc..but how complicated is it?
   

Thanks