As a child I commuted to school on some ancient but reliable and quite satisfactory trains, and I know there are some lines (such as the Island line) where the stock is 40 years old.  The "153" units that predominate on the TransWilts service wer built in the mid 1980s.  However, they're diesel trains and these tend to wear out a bit quicker (20 years life has been quoted) and I was wondering what the plans are that First have for them.

From First's new franchise FAQ:

What are your plans for the current Wessex and First Great Western Link fleets?
These fleets will go through a programme of improvements and interior uplifts throughout the franchise term – including installation of CCTV cameras to enhance passenger security.

I read this as saying that the remaining service(s) will be run with the same trains, overhauled but not replaced, for the next period of 7 to 10 years.

Indeed - if that is the case, it's a sensible plan. There's a lot of things that are very sensible and positive in First's / DfT's plans for the area - just a few "oddball" decisions that seem to be letting the whole show down at least as far as certain customer (journey) groups is concerned.  These tend now each to be special / unique cases with different metrics; in the particular case of the "TransWilts" service to which this site is dedicated, you have a service that's shown rapid growth since it was increased from 2 to 5 trains per day  - ticket sales are up 8 fold in 5 years - being slashed back to that 2 trains a day again.

There's been talk about the reliability of the service and one of the questions that came up related to the stock (broken down trains).  Train breakdowns on the line are, thankfully, very rare , although I was on a service about 10 days ago that terminated at Chippenham and then headed back to Westbury sick.  The problem seems much more to relate to a lack of what's needed to run the trains at Westbury where they start their cycle ... be that crew or stock problems.  As user's we've a suspision that if anything from there can't be resources, it's "The Swindon" that's cut and if the operations staff are faced with terminating a 3 car Bristol service, packed with people coming up from Portsmouth, of dropping our service you CAN understand why they  make the choice they do.

Anyway - summarising.  Yes, if they're going to provide a reliable service through the next franchise period, I'm more than happy to continue to use the 153s which usually form all the services except the early morning one (normally a 2 coach 150 unit). SBL_Forever's specific information on these sets probably "out-trumps" the generic information I have read.

Well - we already have a 153 marked "Central Trains" provining part of the service ... Central Trains, like Wessex, being a part of National Express. I expect that has to go back on 1st April.  I look forward to seeing what comes out of the melting pot as units cascade - and there may be other options that come up too.  The London to Bedwyn service is extending to Westbury - perhaps there will be a chance of those outer London units running some of the Westbury based services in the future now that they'll be (a) run by the same company and (b) on routes that meet up.

Yes - I had a glance ay your site (and I have actually travelled by train from Marks Tey to Sudbury in the past).  Great site ... and an hourly service even on a Sunday that we would kill for. But then, Sudbury had 10 times the ticket sales of Melksham in the 2002/03 stats which are the latest I have country-wide. That's rather like comparing apples with oranges, mind you ... I'm quoting an intermediate station in our case where only about a quarter of the passengers leave or join the train, versus a terminus. .... I'm in danger of making the accountants mistake of getting lost into state here ...

Exactly. In all the differences between each line, that's a common thread.