Thanks for the replies, think I will risk the five minute connection, it's valid, and if it doesn't work, I will get my delay/repay!
You will get a 2 hour delay, as if you miss the 1008, the next Aberystwyth service isn't until 1208. Yes you will get delay repay, but it may be small recompense for such a long delay
I make a similar journey very regularly, often weekly. I use one of the online tools to find the platform number for the TfW train before I arrive into International, so I can go straight to the platform without wasting time trying to find the departure display, and also to check that they aren't starting the TfW train from New St or Wolverhampton.
If my train into International is running late, I look at the map on OTT to see if they are letting the TfW service out first. If so, I stay on my Avanti service to New Street or Wolverhampton in the hope of catching it up. If I still miss it, I will catch the next WMT service to Shrewsbury, as Shrewsbury is a far more pleasant place to spend a couple of hours. Also, a lot of passengers will have emptied the TfW train by the time it reaches Shrewsbury, making it much easier to get a seat at Shrewsbury. And if they are doing a set swap at Shrewsbury, you might even get on the new set before the train from Brum has arrived.
The only problem with joining at Shrewsbury if you are not familiar with the service is knowing which half of the train to join. They announce the front half is for .... and the rear half is for .... but this is singularly unhelpful for a train which is reversing! For Aberystwyth, you generally want the rear half as the train arrives, which will be the front half when the train departs, i.e. the half closest to the massive Severn Bridge Junction signalbox.