Worth pursuing a Big 4 offer that I don't especially want, just for the ACA?

No, don't do it.
If you aren't really that keen now, you are going to jack it in during the 3 years of your ACA so save yourself the trouble.

I have made it to the first interview stage for Deloitte in Transaction Services, but I am unsure if it's worth me going for it now. To be honest I don't particularly want to go into accountancy, literally the only reason I considered it as a possible career was because I opened the Times Top 100 book one day, saw that PwC was at the very top and had been for the past 9 years or so, and therefore must be a good career to aim for. It was therefore mainly because of the prestige that the job has, and I feel that if I took the job it would be more to please those around me than because it's a job I especially want. I mean, I wouldn't even consider going for a role with a firm like Grant Thornton or Baker Tilly, simply because they're not the "elite". Also, having read up on the programmes offered by the Big 4, lots of the information I could find underlined how amazing the ACA is and how many doors it opens. But then again, the only doors it opens would be in accountancy, surely? I have read on forums from many people about how it's common to "fall into accountancy" and then realise too late that they hate their job. I fear that, having these doubts now at this stage, I'll just end up being another one of those people? Is it worth pursuing a Big 4 place and seeing whether I like it, for the eventual benefits of the name on the CV and the ACA?

Ideally I'd like to bag a job related to either technology, general business or marketing, whether it's the grad scheme from Accenture, Barclays or British Airways. Would the benefits of getting a place on these really be so much less, as I wouldn't gain the ACA through it? And just why are Big 4 offers seen as the holy grail of grad jobs, as opposed to those offered by other large companies (apart from banks)?

What a dumb ass, you already know the answer to this.

The ACA is great... for accountants.

Do you even really want a Technology or business or marketing career (because those three are quite different...) or did you just open the Times 100 again?

You can't go wrong moneywise with either. As long as it starts over £25k do something you enjoy, otherwise five years in you'll be thinking 'is this it? Why do I get up in the morning? How do I get outta this well paid rut?'

They aren't really the holy grail of grad jobs just yet, but they're getting there since they've been acquiring well known strategy houses and are expanding towards the consulting industry.

Anyways, Big 4 offers a range of grad jobs (audit, assurance, tax, consulting, advisory, actuarial, corporate finance, and legal services - wiki) and aren't just limited to audit, you may want to explore other services more and apply to those in the near future.

Also, it's doesn't hurt to get more interview experience. You should just keep going with the application process and decide if you really get the job.

Best of luck

If I can be honest, not many people make it through to completing the ACA with a Big Four unless they're committed to it, and reading between the lines, you pretty much sound like it's something you'd rather avoid. You'll be working ridiculous hours (sometimes 7 days a week and often until midnight, based on my brother and all his workmates' experience), being sent to different ends of the country/out of the country with little notice ("oh, you're in Germany tomorrow, plane leaves at 6:30am"), the exams require a lot of work and you'll be mentally and physically ****ed if you're not committed to it.

I'd honestly advise avoiding it unless it's something you want to do. It's a great opportunity for those who want to go into it, and indeed it does open doors (generally in accountancy-related careers, but there are sufficient transferrable experiences to go into a few other fields). I wouldn't say it's a qualification worth pursuing (given the time/effort you'll sacrifice) unless you want to work in the field.

They aren't really the holy grail of grad jobs just yet, but they're getting there since they've been acquiring well known strategy houses and are expanding towards the consulting industry.

Anyways, Big 4 offers a range of grad jobs (audit, assurance, tax, consulting, advisory, actuarial, corporate finance, and legal services - wiki) and aren't just limited to audit, you may want to explore other services more and apply to those in the near future.

Also, it's doesn't hurt to get more interview experience. You should just keep going with the application process and decide if you really get the job.

Best of luck

Yeah I might try applying for some of these other areas instead, and attend this interview in the meantime for the experience. Can't hurt I suppose! Incidentally, would you know if it's be possible to phone up HR and ask to switch my application to another area now seeing as it's all been online tests so far, or is that not possible?