Trying to remember a children's book series

Klorgnum

Every so often, I'll remember this series of books that I used to read, or rather, that I used to read this series of books. I can barely remember anything about it, and it's kind of bugging me that I don't even know what it was called.
All I remember is:
It was science fiction
It was about a guy raised in a warrior society, flying around the universe fighting dudes.
It was unusually violent for a children's book and regularly described people as having their skulls caved in by the main character. I think the primary weapons used in the series were called 'needleguns', but I could be wrong.
The main character was completely comfortable with being naked. This was mentioned in every book.
Humanity had not encountered aliens, at all. However, aliens existed and the main character had one as a companion. I think it looked like a large bird. It may have been psychic.
The author was English, and may have moved to Canada.

I know it's not a lot to go on, but if it rings any bells I'd appreciate the help.

BONUS QUESTION:
Just today, I remembered another children's book I read. It was part of a series, though I only read the one. It was about a bunch of kids who built a spaceship out of parts in a junkyard (in the future, when you can find spaceship parts in a junkyard), and fly it out to go visit their parents who are... somewhere else in the universe? There's a bad guy called "The Octopus" I think, and he's enslaved the parents. On the way, the kids find a derelict ship that had carried radioactive materials. There'd been an accident, and the crew was killed by the radiation. The last words in the ships log were something to do with it being "too hot".
Any ideas what this was? I'd like to know more about the series.

Daenris

Are you sure it was actually a children's book series, or was it just a series you read as a child? Some of the things you mention (skulls caving in, nudity) probably aren't very common in children's books.

There's a list of sci-fi series that use/mention needleguns (or similar) here. It may be one of them.

Klorgnum

Thanks for the link Daenris, but none of the works listed are the ones I'm looking for.
I'm positive it was a children's book. They were shelved in the children's section at the library, and I don't think they were as long as typical adult science fiction books. EDIT: Although it might have been a misfiled young adult book. It was still written for a younger audience though.

Sarcastro

I think you may have been reading something from The Last Legionary series by Douglas Hill. I believe needleguns and vibroblades are part of the lexicon, and the series is young science fiction about a young man raised on a harsh warrior planet, which then sends its citizens out as mercenaries. Keill Randor is a lone survivor after his homeworld is destroyed, and, outfitted with an unbreakable skeleton, travels about the universe looking for answers and indeed, a few heads to bash in along the way.

Although the second book you described is not part of this series, Douglas Hill did write many other young science fiction books, and one of them, 'Have Your Own Extra-terrestrial Adventure' (1983) was published within a year of his primary series by the same publishing company, and would have been in the same section at the same time in your local library.

Edit: More reading, and yes, Keill had a telepathic avian-looking alien companion from another galaxy named 'Glr'.

Klorgnum

Sarcasto: I recognized it as soon as you mentioned the title! Thank you!

RUNN1NGMAN

Hahah...I am in awe of the sheer power of H/A.