Then I guess Malta would be integrated as part of the UK, with representation at Westminster and all that...
This could set a precedent for some other British colonies that went independent OTL to remain part of the UK, akin to the French DOM-TOM...
Meaning that these territories would be represented at the UK parliament, and use the same currency as the UK, rather than a hodge-podge of different currencies (like the US dollar, Euro, East Caribbean dollar, different pounds).
I think the OTL British overseas territories would be represented in this manner, along with some Caribbean and Pacific island territories...
Also, they would be part of the EU if the UK joins...
This could have further effects on Malta, in that they may enter the EU earlier than OTL (2004) if the UK enters like OTL (1973), and that they may use the British Pound today as their currency rather than the Euro...
On the flip side, Maltese may not be the only Semitic language that's official in the EU, as Malta wouldn't be a country...at most, it would have semi-official status like Catalan, Basque, Welsh, Scottish Gaelic, and Galician...
Oh, and Malta would be part of NATO as the UK is part of NATO, and NATO covers the Mediterranean area...