Thanks to everyone who helped in all this. I have some further information following a visit to the dial by the original enquirer in heavy rain on Sunday!
It seems that there is only the second line of the quotation on the dial and that it is as reported. The dial is interesting in that it has two faces at right angles (one gnomon is missing though) and it is topped by a triangular based pyramid. After all this effort it now transpires that the enquirer's son-in-law's uncle (if you can work that out!) is non other than Prof Herbert H Huxley who is now in his eighties (I think) lives in Cambridge UK but for many years was Professor of Latin (or some such) at a Canadian University. Indeed he was the person who wrote the contribution in Encyclopedia Brittanica on Martial! As soon as this was realised he was consulted and he confirms that the two lines of the quotation are the only lines (ie they are not part of anything else) and that in the circumstances of the second line being quoted alone and on a sundial he would translate it as: "Don't criticise the time I give you but publish your own." It does not therefore appear to have special connexion with the brothers or their fate but my contact will telephone the Vicar of the church to see if there is any other information we can obtain. If this proves interesting I shall pass it on. Once again, many thanks to all who have helped identify the message. Patrick
