Hi all. I recently acquired a 303/25 because it was so cheap, but am having trouble finding reloading information. I was wondering if i can just neck size .303 British brass with say a 26-06 neck die, and then just use any 25 cal seating die? or am i going to have to fork out for custom dies? any help appreciated

25-06 die will be too long and too small for one.
a hornady neck die will do the necks and depending on your chamber a 303 die the body.
you'll probably want the short neck die.
there are a couple of different versions of the 303-25 out there.
but after fireforming i'd just neck size and anneal till they got tight then start over with new brass till you run across the die set.

Forming is rarely done in one step and yes, A custom die is needed, try CH4 in the USA or Simplex in Australia at http://www.jansa.com.au/simplex3.php . I purchased my .303/25 die from them.

I have a .303/22, a .303/25 and a .303/270. I have a redding bushing die with a .308 Win body and swap around the necessary bushings. A 25/06 die will be too long in the body for the .303 case.

Making .303/25 brass - start with NEW brass - I use the .310 followed by the .284 bushing and then anneal and then run it through the .303/25 to get the final size. I neck size with the correct bushing selected for the desired size depending on the neck thickness of the brass. DO NOT FL size .303 brass.

Depending on the rifle action, here are some recommended loads - Note: these are for the SMLE MkIII action or the No4. P14 actions can take higher loads. Note: AR2206=H4895, AR2208=Varget, AR2209=H4350.

87gr - AR2206 - 34gr
87gr - AR2208 - 37gr
87gr - AR2209 - 41gr
100gr - AR2206 - 31gr
100gr - AR2208 - 33.5gr
100gr - AR2209 - 38gr
117gr - AR2206 - 28gr
117gr - AR2208 - 31gr
117gr - AR2209 - 36gr