Well, it's sounds like a great goal and something that I'm sure you will achieve. i think that you probably need to take one of the runs out for a week i.e. just do two runs this week. Giving your muscles a break might just help to relieve that heaviness. Another thought; have you changed your diet or time for running? This could have an impact. It is probably just a motivational thing, like you say. If running becomes a real plod then it's time to change something. Perhaps a change of scenary or music or try a new podcast, or a running club, or a park run. Give yourself a reason to run, something as simple as running to a postbox to post a letter seems to help me!
I'd suggest doing something different during one of your 30 minute runs. Try running to a beat if you've not done this before; you could try one of the 5K+ podcasts or one from the Podrunner website. Choose one with short fast intervals or longer, slower intervals with 2-3 mins 'recovery' jogs between. You may find mixing up your pace relieves the 'chugging along'.
Are you able to go somewhere different for your longer run, somewhere further from home? Even if you choose a route that you know will be too long and go prepared to run for 45 minutes and walk the rest of the way. How about an off-road trail - a woodland walk, riverside path, canal towpath...?
Sorry to hear your hitting a wall. I think you could be right when you said you might be over training. As your doing curves as well.(dont know what that is sorry). Your body needs time to recover I would try 1 steady run or interval training which is like running hard for 60 seconds then jog at a comfterable pase for 2 mins and repeat for you 30 mins or so. and devise a bit of a circuit training for exersise day 2 ( or do your curves) theres loads of apps to give you ideas, i do a 5 min walk to warm up, then 30secconds as many as you can of push ups, squats, burpies, leg raises, sit ups, bicep curls ( with bags os sugar) after each one i have a 45 second rest and do the whole thing 3 times then a warm down walk and plenty of streching. Then on excersise day 3 go for a longer run, up beat music, i wrot a bolg about running to music as i found a web site that works out your running speed into music beats so you can find the correct tempo music to run to, and differant route, this may break the monotany and give you the spark to egnite your motivation again. Good luck with your goal YOU CAN DO IT!!
Oh an your so lucky living by the coast, i would love to do early morning runs on a beach watching the sun rise it must be so tranquale an beautifull, embrace your suroundings and enjoy them Good luck and keep running.
Have been fannying around a bit since and have now had sciatica for the last few weeks, but planning to get back out there tomorrow on a trial week one run.
Great to hear. Well done. I'm 55 too... enjoying being properly fit. I constantly battle with tight calves, and think I'm going to treat myself to a massage soon to see if I can turn them back from semi-solid to soft!
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Going Backwards!!
Going backwards
Post graduate run
Going backwards in week 8 
