Going on Gene's experience last year I suggest you purchase another visa- your 3 months stay finishes on the 26th May and you come back on the 27th August- only 1 day out but not worth the risk.
Sorry to hijak this thread We are in a similar situation arriving 5th june for 2 weeks then going back 22nd August for 2 weeks.
Does this mean we will potentially save £50 (2 adults 3 kids)?
Tony you will need to buy a new visa as it only lasts 90 days from the date of entry to the day of leaving.
kirky you will need to renew your visa as well.