By all means go to Bath if you have not been before - but, just a word of advice, it can be rather difficult getting out of Bath onto the main motorway (interstate) that takes you down to the south-west. I would not advise staying Bristol either as it can be very congested and is simply not worth the bother.
I take it you are driving and not using the trains?
I would advise this - places marked * are worth a stop for tourist appeal. Leave Chirk on A5 heading towards Shrewsbury. Then A49 going S. After Craven Arms - look out for STOKESAY CASTLE * on R. Then continue to LUDLOW *. The best view of Ludlow Castle is from the west bank of the river.
Back to A49 & continue S to HEREFORD * = worth a look but traffic congestion can be bad. (Medieval Cathedral). Then, continue S to Monmouth (not worth a look in my opinion). Anyway - take A466 down the Wye Valley & stop at TINTERN ABBEY * (ruin). You may also like to detour into CHEPSTOW to see the CASTLE * - good view from river bridge - walk from castle car park. Then, it is over the Severn Bridge (M48) into southern England - where you will soon join the M5 for the south-west - OR - continue E on the M4 towards Bath - using A46 to reach Bath from M4 J17. (Consider staying somewhere like Chepstow as it will be cheaper than Bath. Bath also has parking issues - you will see P&R signs on approach to the city. This means Park & Ride - where you dump the car & take a shuttle bus into the centre).
If you do go to Bath, when you leave for the SW, head first for WELLS * - which has a medieval cathedral.
Google the places mentioned to see if they are right for you. I am trying to indicate that there are places of interest en-route.
