Wifi connection issues - UK

Operating System: OS X Yosemite 10.10.4

MacBook Pro (Retina, 13-inch, Late 2013)

Processor: 2.8 GHz Intel Core i7; Memory: 16 GB 1600 MHz DDR3

I have moved to a new home (Sussex, UK) using a BT Broadband connection. My MacBook Pro (Retina, 13-inch, Late 2013) keeps dropping the wifi connection, for no apparent reason (all other Apple and PC devices having no problem).

To re-connect, I have to go through the full Network Preferences / Assist Me diagnostics.

The clue seems to be in the following message - but it means nothing to me. Can anyone help?

When connection is dropped, the wifi message reads:

"Wi-Fi has the self-assigned IP address 169.254.227.149 and will not be able to connect to the Internet."

When connected (via the diagnostics tool) the wifi message reads: "Wi-Fi is connected to BTHub4-6MHZ and has the IP address 192.168.1.67. "

All suggestions on how to fix this gratefully received!