I'd recommend using cgarsltd.co.uk.
Firstly, a warning;
Tubes
will not keep your cigars safe. They are for safe packaging, and will only keep them at their best for about a week or so. I do not recommend leaving a load of nice cigars in the packaging tubes up until August, especially not for wedding favours that have cost a fair bit!!!
I'd suggest getting a humidifier pouch, they're cheap and the larger bags can keep about 25 cigars fresh for 90 days or so.
This is perfect:
http://www.cgarsltd.co.uk/humidified-cigar-travel-pouchbag-large-p-3286.html
Now that the safety caution is out of the way, onto the cigars! £5 per cigar isn't a great deal for a nice cigar. Anyway...
Start by narrowing down your choices by getting rid of any full flavoured cigars. Any guest that hasn't smoked before, might not like the experience at all. It's like drinking a mug full of espresso, when you only like caffè latte. I'd recommend getting a mild or medium flavoured cigar. I know people have suggested Bolivar already in this thread, and it's nothing against them, but I don't think these are suited flavourwise to beginners who might be put off by the overly strong taste.
As for size, a 5 inch cigar is somewhat a standard size for a beginner or casual smoke. I'd recommend looking at petit coronas, don't go too thin, but don't think that you need to go and buy a seven inch Winston Churchill thick-as-your-**** cigar in order for it to be good!
My recommendations:
http://www.cgarsltd.co.uk/montecristo-cigars-p-157.html
The Monecristo No. 5. It's a nice all round cigar, very popular for novices but it's also one of the most popular cigars in the world for aficionados too. It's a little bit smaller than it's big brother the No. 4 - and given the budget I'd say go for the No. 4 - at 4". Don't be put off by this though, smoking normally and savouring it will still last a good 20-30 minutes.
The price of 25 works out at about £7.40 per cigar.
The No. 4 on the other hand is the most popular cigar in the world, and rightly so. Ignore any reviews of this cigar saying that it's "best years were in 06 and 07, the fact is unless your guests have got one to compare or are aficionados themselves, they aren't going to care in the slightest. You have to be a real expert to even notice (I'm not saying I am, it's just logic), and of course have the budget to buy the comparisons!
http://www.cgarsltd.co.uk/montecristo-cigars-p-153.html
The No. 4 is measured at about 5 and a bit inches, and costs about £9 per cigar. Over your budget I know, but totally worth it! I've just bought a load of No. 4's myself, you'll be hard pushed to find anyone that doesn't like them (of course only if they like smoking the things in the first place).
Finally, the Cohiba Panetelas. It's a half corona size at 4 1/2" but nothing else comes close at this size and price! Just read the reviews on the website. It works out at £8.30 per cigar. I'm sure you could probably haggle a lot of tobacconists down.
http://www.cgarsltd.co.uk/cohiba-panetelas-panatelas-p-69.html
Good luck! Hope this helps.