OK, so some of your questions are pretty simple to answer!
Firstly - yes, it’s really common to have multiple pensions as you move through your working life.
I’ve got 4 from one single company, as the rules changed for them during the time I’ve worked there! I get 4 different statements, although they do consolidate that and total it for me!
Next question - can you merge them?
Not all, in the cases you’ve given.
Do you understand that - lucky you! - your Civil Service Nuvos and Alpha pensions are “Defined Benefit” schemes? This means that there is no pot - so when you say you’re trying to find that out, what do you actually mean?
With a DB pension, what you have is a promise to pay you a benefit that has been defined in advance - that is, the annual payment that you describe. There is no pot of money allocated to you. Don’t worry about what happened to your contributions, trust me, they were tiny in comparison to the benefit you are promised!
You can’t merge these two. Not least because it would be madness! Nuvos is better. Actually, they’re not massively different depending on your age, but for example Nuvos pays out at 65, Alpha not until your state pension age which might be later.
You can’t transfer your later Aegon and L&G pensions (both Defined Contribution) into your old civil service schemes.
You also can’t transfer the Civil Services into the new ones:
(1) because you’d be off your bloody rocker to do so!
(2) because no IFA would sign it off (transfers from DB to DC need IFA approval) because of reason (1)
(3) you’re actually very limited in transfers out from Civil Service anyway - they only allow transfer to a very few number of other schemes, called “the Club” - some other public sector DB pensions. So actually (1) and (2) don’t apply - I’m just making the point that you’d be crazy to try even if you could!
Back to your DC Aegon and L&G. DC means there is no defined benefit promised at the end. What you have is a pot of money that is invested hopefully for growth. In this case, it really is a pot - an individual account in your name that you can log in and track often, or at least you have a legal right to an annual statement.
Should you combine them?
Firstly - you might not be allowed to, each scheme has its own rules about, “transfer in”. But often you can.
Secondly - should you? If one has more expensive fees, possibly yes. But you may like the spread of risk if they’re invested differently.
I’d say your action should be to find out those management fees and take it from there.