Servicing depends on what you are doing and how you care for your equipment but is well worthwhile if you anticipate a long reliable life from your housing. Obviously, the manufacturer should be able to bring a housing up to full spec but the are independant repairers who can do so too. If you are careful with your housing, wash it well to remove all salt , dry it and keep it free from sand and so on, then it will need less servicing. If on the other hand it is used heavily and extensively, and especially if it is used in chlorinated water, it will need more frequent servicing. A FULL service involves stripping a housing down to inspect each seal so they will be replaced as its not worth putting a used one back. A FULL housing also should replace circlips and weakened springs too, so its not just about seals. If any control feels as though it is no longer operating smoothly or if it feels as though it is being tugged back (by a dry 'O' ring) then its time for a service/repair.
This topic has reared its (ugly or ridiculous?) head once again with an article by Neil Garrick-Maidment of the Seahorse Trust on page 122 of the November issue of Diver magazine in which he again suggests that flash photography is a problem for seahorses.
In it he comments about 'a very small group of divers' who 'tried to suggest that natural light is the same as flash, and that flash does not kill seahorses" which I suspect is a reference to myself amongst others and whilst badly worded, in that in my opinion it gives an incorrect impression of what actually happened, goes on to say 'They challenged MMO [the Marine Management Organisation which has banned the use of flash photography of seahorses in England] to prove that it does" which again is not quite the way I remember things - unless you consider that carefully worded emails to the MMO, which were basically designed to be informative, to be a 'challenge'. Interestingly a recent paper by Harasti & Gladstone in the Journal of Fish Biology entitled “Does underwater flash photography affect the behaviour movement and site persistence of seahorses” which looked at Hippocampus whitei, a not dis-similar Australian species, found ‘negligible effects’ (even following additional handling as well as flash photography) on the seahorses, and far from suggesting that flash photography should be banned, suggests that it is in fact a potentially useful tool for obtaining scientific data.
I wonder if the two are linked or simply co-incidental?
I'm not sure that you have sufficient data in the images for an absolute ID to be made either - the most useful guide I have is "A key to Crabs and crab-like animals of British inshore waters" by John & Marilyn Crothers (an AIDGAP guide from the Field Studies Council). Differentiation often relies on relative lengths of leg parts, so you need to take photographs bearing this in mind if you want to be able to identify them.
Its not a worm its an echinoderm - a 'wom-like holothurian' to quote Bernard Picton! Labidoplax digitata, and its fairly common off Criccieth - it is actually found on all British coasts, but Criccieth is by far the best place to see them that I've found. They reach out from their holes to scavenge detritus within reach and retract quickly if disturbed.