Thanks for the replies people.
@ Mardie Sounds good. I hope you'll keep us up to date on how you're doing. When I was previously losing weight with Spark, I was aiming to do a 10k race [walking not running] with a friend. Both of us were used to walking a lot in our daily life, so we decided we'd do it in the fastest possible time we could manage. I guess that kept me training on the treadmill even when the weather was poor. The day of the race was scorching hot and we had a fantastic time. Naturally we run [well, jogged] the last few hundred metres. Actually, it was a couple of months after that I kind of went off the wagon. Maybe you've hit the nail on the head and I need an extra target as well as losing weight and getting healthier.