16f818 - 16f819 compatability

Apologies if this is a daft question but I am very new to this and so am stuck on the PIC i've been using so far the 16F818, I am not able to order this one from my usual supplier as they are out of stock until 19th December but they have the 16F819 in stock, having looked on the Microchip website it seems the only difference is that the 819 has twice the KBytes of the 818. I have a program that works fine on the 818 will I be able to blow that straight into the 819 and will it work without any alterations to the code?

Your program should work directly in the 819 unless you are using banks 2 and 3 on the 818 to access bank 0 ram. Look at page 11 and 12 on the data sheet.