Even in the coldest weather, the ground rarely freezes below 10" - 12" deep here in the states. You may be able to search the internet and find how deep the frost line is in your area.

When I was in Blackstone, MA., I recall the required depth for water piping on the project I was working was 18". We found that the ground there, in February, was frozen only to a depth of 8".

Once you get below that frost line, digging should be a bit easier.

I have a ground mounted HF6V, and I guess you'll use the supplied mounting pipe like I did. It's pretty small in diameter, perhaps a rotary drill designed to drill masonry and concrete would do the trick. They make bits for the Hilti brand drills quite long, and quite large. Maybe check a local tool & equipment rental center?