Just go to Citroen , give them your reg no /engine details, pay and thank the man.
Not sure how many washers the 1.8d has but while you have pulled the injector I would change all the washers.
Took it to a company called 'SIS' (specialized injection services) and he said that two of the injectors would need refurbing - the diesel was not leaking via the bottom as i thought but was leaking from below the top bolt and dribbling down making it look as though it was leaking from the bottom thread when it was not - anyway for £90 he's going to take two injectors out - refurb them and then replace all 4 seals anyway. I phoned a fair few garages and they all said 'no, I don't really touch injectors' and after trips to eurocarparts, GSF and citroen themselves I got no where in purchasing just the seals (unless I wanted a pack of 50 from citroen lol) but thanks for your help guys, no doubt in the near future i'll be posting some more issues i'll have
Just a follow up, I had two of the injectors reconditioned and the leak has now stopped, although he did find a leak in the 'top casing of the throttle body' and to be fair I dont know how I didnt see it before - anyway its sorted now so a thank you to everyone