Q: how to send imessage and face time from malaysia to London?

You'll need to add the prefix for UK (0044 or +44)

iOS: Using FaceTime , iOS: Troubleshooting FaceTime and The Complete Guide to FaceTime: Set-up, Use, and Troubleshooting Problems might also help to set up FaceTime for you.

When using iMessage, if you type in your friend's phone number, after waiting a couple of seconds, the "send" button will turn blue if that phone number is linked to an iOS device and can recieve free messages through iMessage. But besides that, I would type in the number you were given