Under the current CAA regulations SLMG/TMGs, SSEA/SEPs & microlights are all variations on a theme; a licence & experience in one can be credited towards the issue of a licence/rating in another with varying degrees of generosity.
Once the EASA rules start, SLMG/TMGs and most SSEA/SEPs become EASA aircraft and will, by April 2015, require the pilot to hold an EASA licence. Microlights will stay out of the EASA system & can be flown on an NPPL(M) but any microlight experience will not count towards the issue of an EASA licence. You could have 1,000+ hours on a high performance 3-axis microlight but if you wanted an EASA licence, you would still have to go through the full syllabus like any other newbie.
What I don't know is when the CAA will stop issuing an NPPL(SSEA) on the basis of an NPPL(M) + additional training & test. April 2015 will be the cutoff for turning an NPPL(SSEA) into an EASA LAPL(A) so you might have 3 years to go from microlight to EASA licence. OTOH the CAA might stop issuing NPPL(SSEA & SLMG) entirely after April (or July) 2012.
Try asking in the forum on the
BMAA website. They will also be able to advise on using a microlight licence abroad - people have flown around the world in microlights.
How long it takes you to get an SLMG or microlight licence will depend on your aptitude. I would expect the average person to be able to do it in your 2x2 weeks timespan, unless you're unlucky with the weather.