Here are some fairly recently acquired items relating to Bristol, starting with a Mulready envelope sent in May 1841. It was adressed to Cholwell House, the residence of the Rees-Mogg family from 1726 to 1941. It was marked as "Gon away not know weare" and received a rare "W"in a circle Inspector's mark.
The next item is from December 1847 and was sent from Chew Magna to Wells, with a "CHEW-MAGNA" udc and a Bristol Penny Post dated handstamp - the year in the date has an inverted "4", which is known between October 1847 and March 1848.
Moving on to August 1874 the envelope below was sent from Bristol to Bordeaux and was franked with 3d. This was the rate for prepaid mail up to ⅓oz, but it would seem that the cover was more than ⅓oz so was liable to the next higher rate for up to ⅔oz and for not being fully prepaid.
The rate for un-prepaid letter was double, as was the rate for letters between ⅓ and ⅔oz. An un-prepaid letter in this weight rate was liable to 12d postage (6d if prepaid rather than 3d, and 12d because it was not prepaid), and was marked with "9" to pay (as 3d had already been paid). The addressee in Bordeaux would have been liable for 90 centimes.
The "INSUFFICIENTLY / PREPAID" cachet would have been applied in London; a framed "INSUFFICIENLY / PREPAID" cachet was issued to Bristol in February 1879, but there is no record of it being used.
This next sheet shows examples of the "BRISTOL / LATE.FEE" duplex cancel, known used between January 1889 and May 1894. Examples of this cancellation are rare, especially on cover.
Finally here is an item sent from Filton to Stockholm in 1960. It was under franked at 3d and received a hexagonal "T / 21C / F.S." cachet indicating postage due, a green Swedish tax label, and on the reverse an "INSUFFICIENT / POSTAGE PREPAID / PLEASE ADVISE SENDER" cachet. The Tax hexagon and the Insufficient postage prepaid cachets were probably applied in London.