Is there any point in topping up my 2013-2014 ISA? I don’t think there is and I should just put the money in a 2014-2015 ISA whilst I can, but I’m not very good at this stuff…

depends how much you are thinking of saving. The key advantage being that you have time to max out this years allowance (should you wish), before starting on next.
In other words if you plan to save more than next year’s allowance, get some of it in now.

Is there any point in topping up my 2013-2014 ISA?

A bit late isn’t it? You should have done it last year.

The allowance increased in July 2014 so I can put more in, what I dont know is if there is any point, and I should just put it into a 2014-2015 ISA in the next couple of weeks whilst I can.

If there is a chance that you will have enough to fill the new one put it in the old one. If you won’t have the cash for the new ones limit don’t worry about it.

It’s always worth putting some money in because if you don’t contribute to it for a full tax year, further contributions to the ISA can be blocked which means a minor admin problem to unblock it.
I found this out last week

You cannot add anything to your 2013/14 account, regardless of whether you used your allocation at the time or not. Once the 2014/15 year started last April you were limited to the amount for that year. If you still have allowance for 14/15 (and as you say it did rise mid term) then whack it in now before the end of the month and you can then still decide if you have enough cash to fill your quota for 15/16. Unfortunately with ISAs it is a case of use it or lose it each year.

You cannot add anything to your 2013/14 account, regardless of whether you used your allocation at the time or not

This is what is confusing me, there is a big flashing “Top Up” button on my ISA account even though I opened and filled it in March 2014 before the April cut off.

Then you must still have some 14/15 allowance outstanding??

yeah not put anything in for 14/15, just the initial amount that maxed it out for 13/14 in March 2014.

I thought it was only one year where the interested was generated over and then it dropped to a silly low rate?

I did say I wasn’t very good at this stuff!

The interest rate does drop but its still tax free, and you can transfer old ISAs to new providers. However the best interest rates seem to be only for newly opened ones, they exclude transfers.

If you have maxxed out even one years allowance you must have around £15 (depending on the rules at the time) and if you are concerned about the interest rate being very low then you should move it somewhere else. You can do this any time.
By moving it you can make a significant difference to the interest rate. Even if you never contribute again, by moving it each year (it is a simple paper exercise) you could buy yourself a new bike in a couple of years.