Scope Eyepiece

Hi,

I have just bought my first scope, Europa 250 F4.8, from Orion Optics (uk).
With the scope I received two Plossl eyepiece (25 and 12.5mm).

I would like to buy some additional eyepeice(s) / tools but after trawling
around the web and newsgroups, confusion has set in.

What should I invest in first? Eyepiece, Barlow, Collimator?
What is a good buy and what would be a waste of money?

I was looking at 4mm Plossl eyepiece (make ???), 2x Barlow and a Cheshire or
Laser Collimator.
(Is it cheaper to buy from the US, as the exchange rate it in our favour.)

Thanks in advance.

Howard