when you talk about a flexi package i assume you mean booking flights and hotels separately.
if so, to put it simply,booking with a proper bonded package will ensure that you will get a full refund if the company goes bust before you go or you will be brought home at no cost to yourself if it goes bust while you are away. you will also have a company rep in resort who should be able to help you.
if you book separately, then you only get back the money for the part of your holiday affected. so if your flight gets cancelled then you still have to pay for the hotel you probaly cant use.
now this is a very simple analysis. there are exceptions to the above, insurance you can take out and other things you can do in advance to minimise possible problems.
if it is your first holiday abroad then i would recommend taking a package for the security it gives you as not everyone is able to deal with a crisis in a foreign country, especially if they have never been abroad before.
although booking separate elements can be cheaper, you need to work out the total costs including transfers to your hotel and see if the saving is worth the hassle.
you should also have some contingency plans if you are booking separately, including a plan to get home if the airline goes bust, a plan to get emergency money immediately if you are left in resort and any relevant phone numbers you may need. you should also ensure your mobile will work abroad.
whatever else you do you should also ensure you have an EHIC card AND insurance as soon as you book your holiday.

Sound advice from Jim.

If you go on a package holiday you are covered by package holiday legislation which menas that if anything goes wrong they are obliged to get you back to the UK somehow, delays due to incidents like the ash cloud la package operator would be legally bound to look after you until you could fly.

Things are ess clear cut if you book a dymamic package (Flex package) ie a flight & hotel through a 3rd company. Any one of those 3 entities could not work out, airline could go bust, the hotel overbook, close for refurb at short notice etc.

You have to weigh up the pros & cons though as for the prices of say 5 package holidays you maybe could have had 7 dynamic package holidays. It could be worth the risk, only you know really.

If you want to read experiences of how people have been treated by 3rd parties when things go wrong things you might want to look at threads about the former airline XL , Holidays 4U, Aegean Flights etc all going bust & how people managed these situations.

Doe

I have done both over the years though the kind of holiday was what made me decide.
When going away as a family with kids i booked a package as i didn't really want to be stuck abroad not knowing what would happen if an airline went bust and how it would upset my kids being stuck at an airport indefinately.
Going away on a lads break we didn't care. We booked it all separately as our attitude was, a gang of us would make our own entertainment and providing we had some money left would just take the delay as an extra few days away.