I've interviewed for and been offered a position with a local company (charitable sector). It's a part time position which is low paid, working with service users on a particular project (job A). References and DBS checks are currently being obtained with a view to starting next month (latest information from the HR department).
I was showing my son the details about the charity today (on their website) when I noticed that they are now advertising another part time position which is much more in keeping with my professional skills as it's a position involving training staff at their venues. The job is still part time although 6 hours more per week but the pay is approximately 3 times more.
Job B is much more my preferred role and one which I am professionally qualified for (education sector, to post-graduate level) and if it had been advertised alongside job A, I would have chosen to apply for job B instead.
However, as I have been offered (and have accepted) the position of job A, I'd like to know if there is any required etiquette regarding the position I find myself in. I really don't want to alienate the company and I certainly don't want to appear fickle, but I am gutted that my ideal job is now sitting there and I feel like I can't apply for it as I've already accepted job A, although I haven't started yet.
I got on extremely well with my interviewer, who told me that I was by far the strongest candidate for job A. The position was available at two different projects and she gave me my pick of project to reflect how keen they were for me to take the position which suited me best, so that I would come and work for them.
As a bit of additional background, it might be useful to know that I was really happy to have been offered job A, as I have been working as a self employed freelancer whilst recovering from chronic illness. As I find working from home too isolating, I have been seeking part time roles which would involve me using my professional qualifications but still allow me to be able to pace myself back into the work place. Jobs with this charity are few and far between and as I am extremely grateful that they have been so welcoming in offering me job A, I was more than happy to settle for it. Unfortunately now that I've seen job B my head is full of "what ifs ..."
I'd be grateful if anyone could offer any insight as to whether I should consider asking them about job B or whether I should just forget it, start job A and then see what opportunities arise later. I certainly don't want to cause a problem for the company before I've even started working for them and I'm not actively looking for an alternative to the job I've been offered, I just happened to spot it. I'd really appreciate others' thoughts about the etiquette surrounding this situation.
Edited to add: The closing date for job B is after I expect to have started in job A, with interview dates advertised as being fixed for the following week.
Thanks for your time and your help.