Seen this reported in the local press. Free entry for those with BS or BA postcodes to loads of tourist attractions on the weekend of the 5th May.
You apparently need to register on the link and they then release tickets on the 21st April @ 10am. I can imagine demand will be high particularly for the likes of the ss GB etc.
In Bath – Holburne Museum, Roman Baths, Fashion Museum, No 1 Royal Crescent, Victoria Art Gallery, Herschel Museum, Beckford’s Tower, The Edge Arts, Museum of Bath Architecture, University of Bath, Bath Racecourse.
In Bristol – St George’s, Natural Theatre, MShed, Bristol Museum and Gallery, Bristol Old Vic, Arnolfini, Colston Hall, Bristol Cathedral, Spike Island, Festival of Ideas, Watershed, Brunel’s ss Great Britain
There is also discounted travel via bus available.