Advice on eye pieces

Dear All

I have a Skywatcher 130P (650 focal length) which came with 10mm and 25mm
eye pieces.

I bought a X3 Barlow to compliment these I and get reasonable results (now
that I've learned a bit about collimation - thanks for the help!). I have
noticed however that planets still seem small even at the higher mag and
I've heard that this is more due to the quality/design of the eye pieces
(modified Keller I believe Skywatcher use). If anyone can enlighten me
further I'd appreciate it.

The main purpose for my post is to ask advice about an addition eye piece
and possibly some lenses for my scope. I'm particularly interested in
planetary and lunar observation plus I would like something that could help
me make out galaxies or nebula better. Bearing in mind what I have currently
(and that I'm on a budget!) please can you advise as to my best options.

Thanks in advance and clear skies

Steve