Hi,
1. In the configuration of each shipping method, you can set restrictions to which they apply, incl weight and/or volume. This way you can limit shipping methods to products with certain sizes or weights.
See the documentation:
hikashop.com/support/documentation/integ...form.html#additional
Edit:
I may add that you could also use "Zones" (and restrictions again, accordingly) to further reduce the number of shipping methods displayed, so that a customer sees only methods relevant for his location. In your case it seems you'll need 3 zones: UK, Europe (except UK), and "Rest of the World".
See here:
hikashop.com/support/documentation/integ...ashop-zone-form.html
2. Since there is a thread for this already, it'd be nice to keep that discussion there to avoid confusion.