Thanks to Clive I'm just about there but struggling on the Capacitor selection The transformer is 300VA and its giving 40VDC (after the rectifier) so 7.5A max

If I follow the online designs and aim for 5% ripple at max current then I need A 37,500uf Cap which is quite expensive and much larger than my other PSU's. 10% ripple is better @ 18,750uf but not sure if 4V ripple is acceptable.?

Assuming that it wont be running flat out and the working current is likely to be 5amps then the ripple with 18.750uf would be better than 10%

Given that most of the ready made ones use a much lower values I can only assume that they have high ripple voltage and it doesn't matter. Am I over thinking this And anything over 10,000uf will be ok?