for what?
The cost has relatively little to do with whether you are a sole trader or employ 250 people. The cost comes from what exc class you want/need and how far away you currently are from fulfilling those requirements. The TWI certification ltd (the biggest notified body regarding en1090 in the UK) charge a rate of Around £595 per day and average requirement is 5-6 days spread over 3-4 months providing your not starting from complete scratch for exc 2.
If your a jobbing welder/blacksmith and your asked to fabricate a I beam or simerla by a builder for a particular Job then you would be exempt from en 1090 as it's a one off and providing it met local planning/building authority inspections it would be ok. However if you offer fabrication of structural steel work as part of your business in a general sense to anyone and everyone then you will need to be en 1090 compliant. Most cases in the UK will fall under exc 2 and for that you need qualified welding procedures in place and as a welder need to be coded to en 287-1. You need a FPC in place which details the everyday running of your fabrication business from when stock comes in as raw material to when it goes out as a finished article and also need to have some sort of responsible named person regarding the quality/traceability of the welding operations. That can all be done by the same person if you are a sole trader. Part or the compliance is the calibration of the welding equipment and that depends on the type of job your welding. For example if your working on high strength steels (355 etc) where heat input is important then your kit would need to be calibrated within 2% tolerances but if heat input is not critical as is the case with 255 and below then a range of 10% is ok as far as I understand it.
It's not a case of saying that everything you've done up until now is rubbish it's just a case of demonstrating how what you do complies. Don't be scared of it, just give them a call and they can Answer all and any questions you may have.
my bad ...I was just passing on experience from when part p got introduced.
So will I need any of this ?. Everything I make is a one off or a modification/repair, for me to get into this EN1090 would cost far more than I would ever earn from it. I'm a sole trader and structural steel work/welding only forms maybe 20% of my business when there's nothing happening with the agricultural work.