It seems to show a Warrant Officer [ three buttons on sleeve and no lace rings and allowed a sword ]- from the 19th century - 1870-ish perhaps?

Unfortunately no such thing as a 'crew list' exists for RN warships.  An individual's Service Record should show the ships they served on

This gentleman is an unknown ancestor but I hoped that being able to roughly date and identify the rank of the uniform might give me an indication of who he is. Thank you in advance!

How might I go about finding a crew list for that period?

Bellona was a small [3rd class] Cruiser and in 1901 under the command of Captain Hubert Grant Dalton, was on Fishery Protection duties and was based in Iceland between April and October of that year, to oversee the large number of fishing trawlers that used the waters between Iceland and the Faeroes. 
As an aside, she visited the isolated community of St Kilda to carry out the Census of that year....

We have some old photographs which have been passed down in the family, a few of which must relate to numerous ancestors who served in the Royal Navy but we are not sure what the connections are.
This photograph is one of about 4 which are mounted on cards with a photographers name Eymundsson, Reykjavik. Another photograph shows crew members on what look like Icelandic ponies. I would be interested to know what anyone makes of this group photo.

So far I haven't found a family service record which includes the HMS Bellona. A great uncle's service record shows he was a boy on the St Vincent in 1901 which I believe was a training ship at that time. Would that have involved going on other ships?
Would the HMS Bellona have been around Iceland?
Could the 1901 relate to something other than the year?

Any pointers or directions for research etc would be appreciated as I am new to this!

A Service record shows who  administered his pay and paperwork – he would not necessarily have actually physically been at the shore establishments shown …
The service record extract you posted shows -
PEMBROKE IV [ Grove]  Jan 42 to Apr 42
NILE [ Grove]     Apr to Dec 42
ASSEGAI    June to December 42
TANA [Express]   from December 42
EAGLET [ Express]   from Feb 43

Note: TANA was at Kilindini, Kenya, and was an accounting and admin base

So Pembroke – Nile – Tana – Eaglet, he was probably never there,  they were just the admin bases.   As for Assegai, although they looked after his pay etc between June and December 42,  the P & V shows that he was only there in October and November.


The P & V shows where he actually was –
 GROVE     January to June 42
SPHINX   June – July 42
Detached?   3 days in July 42
AFRIKANDER IV   July – September 42  [ one day on detached duty]
ASSEGAI    October – November 42
EXPRESS    from December 42

I can’t see any slot for being a prisoner

Thank you.
Any chance you might have some insight on why the payroll sheet would have so many entries and movement during the same time frame that his navy record just shows HMS Grove to HMS Assegai to HMS Express?  I'm really struggling to make sense of these six months.  He was a POW and said he was saved by American soldiers.  This six month period is the only period that I can see that happening.  No mention of being a POW on any of his paperwork.

Mmmmm,  not sure about this

The ‘SS’ prefix to his service number shows this chap was a Short Service rating.
Joined in October 1921 and discharged to Shore in Oct 1926 having served on several destroyers [Tuscan – Serapis – Raider – Campbell) and one cruiser [Yarmouth]
His rating is shown as Able Seaman, but he seems to have qualified for Petty Officer in 1923, although I cannot see that he was rated.   Remained in the Fleet Reserve (RFR)  from 1926 to 1938; 

PEMBROKE – naval shore base/barracks at Chatham

GROVE    - escort destroyer – torpedoed in the Med in 1942 – see:
https://www.naval-history.net/xGM-Chrono-10DE-HMS_Grove.htm

SPHINX – camp at Alexandria, Egypt

AFRIKANDER  -  naval shore base at Sinonstown, South Africa

ASSEGAI  - naval training base at Durban, South Arica

EXPRESS       destroyer; serving at that time in the Indian Ocean –
    https://www.naval-history.net/xGM-Chrono-10DD-21E-HMS_Express.htm

AMEER  - escort carrier
https://www.royalnavyresearcharchive.org.uk/ESCORT/AMEER.htm

ASBURY  - accommodation at Asbury Park, New Jersey USA

AVALON  -  naval shore base at St John’s, Newfoundland, Canada

AVALON III  - naval shore base at Argentia, Newfoundland

COCHRANE  - naval base at Rosyth

MAYINA  -  transit camp at Colombo, Sri Lanka

DIYATALAWA – site of rest camp in Sri Lanka

Re: LENT - you are correct, it means that he was briefly loaned' to another ship or establishment for short period
Re: DUTY – This has been raised before, and not satisfactorily answered – I think the general opinion is that it meant ‘detached duty’, perhaps with a working party, basically somewhere that was not a 'regular' establishment