Opportunity

The guy that sent Me the huge bunch of flowers, He's called 'M'. And he likes me, alot. He was dumped by his Gf of 6 years around about the same time that I split from Bf, so my immediate thoughts are 'rebound'. And I can hear very distant alarm bells....very distant, almost inaudiable in fact.
He said He needed a friend who was going through a similar situation as Himself with the breakup so we got chatting and started to meet up for drinks/cinema/his sister's wedding etc. He's really nice, almost every girl at work would love to be held in His affections. He's funny and maybe a little shy, polite, kind and loves running. He's entered for the London marathon next year. He's only 5' 8'' tall and I tower over Him in heels :) He's neat and tidy, good at cooking and has a cute sense of humour. He likes My brutal honesty about the way I look, finds My hatred of prawns amusing, loves My lol-cat and can hold sensible conversations with My son. I think He's about 2 years older than Me, so mature but still with a desire to teach Me how to skateboard :S He wants to go everywhere and be busy most of the time, He does'nt like being sat around doing nothing. He seems the kind of guy that would want a steady Gf with possible marriage and kids in the future. And He is perfect husband material and would make a doting father. He said that I have become the closest thing He has to a best friend at the moment.
so why do I feel nothing for Him?? How many times in a girls' lifetime will a guy like this walk up to her and say 'I really like you' ?
My workmates think I'm retarded and that I should just jump into bed with Him, but I just don't feel that way about Him. He keeps saying that He really likes Me and I have said that I like Him as a friend and He said He's cool with that. So I'm not leading Him on, but I still feel guilty that I might end up hurting His feelings. I think to just keep being a supportive friend to Him is good for now, who knows what the future might hold?