local & international shipping by weight, offerring different postage rates

I've been searching for a solution. I see faq info on flat rates and zone rates and copy tables, but i still do not see a solution to my problem.

I'm posting from the UK. Right now I'm using paypal and can only offer one flat rate to all customers for postage.

I want to be able to offer (based on customer's address details) 1st class, 2nd class and next day delivery to UK customers. To my international customers I want to offer them the relevant surface, airmail and 'traceable' postage cost options - not just an international flat rate as Royal Mail has different costs for each destination.

This will be based on final weight, not individual items.

Is this possible with my limited programming knowledge or should I surrender now and pay someone to do this for me?

Thanks

Holly