Welcome back to pony collecting
Normally the shipping prices charged by members here are nowhere near as expensive as those on ebay since a lot will still ship first class, and they dont charge crazy high handling fees- so dont worry
Shipping from the US to the UK first class is usually pretty reasonable . If you do buy a more expensive pony/ponies it would probably still be best to pay the extra for priority with tracking though to protect you and the seller
Australia is normally pretty reasonable shipping to the UK - I think around $10-$12 for 1 or 2 ponies together
Canada is more expensive to ship from than the US and Aus.
Europe is more difficult to quote prices for since the costs vary from country to country. Some places are reasonable, but others can be expensive, so dont be surprised if there are big differences in prices from sellers even in countries that seem close to each other