long runs back to back -better alternatives

No... the day after your longest run of the week would ideally be a rest day or some form of "active recovery", like an easy spin on the bike or an easy swim. A good training plan will lay that out for you (there are some good ones here on BT).

Thanks - think I kind of fell of the following a plan thing a while ago. Following a very basic plan now for next few weeks until my race. However unplanned rest day yesterday has thrown the plan out of kilter!

hannahs - I see you are a gold member.  Doesn't that level of membership allow you ask a coach? 

Ah yes that is true as well and again I confess I've not made best use of that in last few months!

Keep thinking that once I've got my first race done then I will regroup and have a think about what I want to do and what plan I'm going to follow.

Did start following a plan at the start of the year but it all got a bit much. Was going to give up but decided that wasn't the right thing to do so I had to go back to basics - set an 8 week plan myself which I figured would be the bare minimum that would enable me to make it over the finish line.

Unplanned rest days happen. General rule of thumb is if it's not a key workout (like your longest run or bike, or a brick where you are focising on transitions) go ahead and just skip it. If it is a key workout, bump it to a day where you can fit it in and scratch a less important workout.

If you miss more than two or three workouts in a week, depending on how far out you are from raceday it's a good idea to re-work the rest of the plan.