Work permit extension

I will need a 1 1/2-month extension to my current WP/LTR, as they both expire 2 years from the date I entered the UK, rather than the date I started my 2-year contract.

I am going back home for Christmas one month before my WP/LTR are due to expire. If I get an extension to my WP before I go out, can I get entry clearance in my home country?

Alternatively, as it is only a 1 1/2-month extention can I get leave to enter at the port of entry (I am not a visa national).

Hope someone can help.