Language Study and part time work

I'm looking into studying Japanese and trying to find a language and also part time work while out there to fund myself

I'm aware I'd need a student visa and would only be able to work a maximum of 20 hours which is fine.

I know of GoGoNihon and if I'm correct, they help with applications for your chosen school, visa, accomodation and even help with finding work.

How good of a company are they?
Are there any other companies that offer the same services, or better?

Thank you in advance.

Note that to be granted Student visa, you will need to show to Immigration that you do have sufficient funds to support yourself.

Also I believe it is a max of 28 hours per week.

I believe that the school that you study at will be able to help with visa, accommodation, and part-time work as appropriate. You might want to inquire with the school that you are interested in.

I'd need a student visa and would only be able to work a maximum of 20 hours which is fine.
Who told you that?
If it was the agent you mentioned in your question, I am sorry to say that agent is not trustable.
Basically you are not allowed to work with a student visa (it is illegal).
You will be allowed to work up to 28hours/week provided that you get a permission called しかくがいかつどうきょか.

If you really want to study Japanese in Japan, please be careful with schools and agent that offer you a job or help with job hunting, they often make money, being related to illgeal job agent.
It is mentioned in this thred as well.
http://www.japan-guide.com/forum/quereadisplay.html?0+155947