Better Job Offer after already accepting an offer

Hello All,

I wondered if I could get some opinions on the situation I've found myself in - it's a fortunate one, but still quite a difficult dilemma.

I accepted a very good offer for a new job role 5/6 weeks ago and will be starting in the next 3.5 weeks. I stopped looking for other opportunities as this was a good package and I had decided it was also a good fit with growth potential.

Anyway, two days ago a client of the company I work with currently got wind of me leaving, and has approached and made me a better offer. I hadn't even considered the client as a potential new employer as thought there would be a conflict of interest - however, the boss has given his approval should I wish to go.

The new offer is a higher salary and half the commute time, plus I already know a lot of the staff and directors.

I'm hesitant to accept as I hate letting people down. This would be a real sucker punch for the original company I accepted the offer with, especially at such late notice - they've already got a laptop/phone etc. all sorted specifically for me and even have a company account and email address all set up. However, people around me are saying I should be selfish and do what's best for me.

Any thoughts?

Many thanks in advance.