WELCOME to FT!!
Summer IS the high season to Europe with airlines AND hotels.
You also do not mention if you have any frequent flyer program affiliations that you wish to honor with your flights. (I do not have experience with the cheapflights but some of the super super low priceline type fares DO NOT accumulate airmiles and cannot be upgraded).
Speaking of upgrade, you did not mention that as a requirement. Cuz I should think a lot of upgrades out of DFW for the high tourist season are already going to be grabbed. Look at your desired airline for more information.
Additionally, hotels may be on the expensive side at the height of summer travel. You also do not mention hotels.. am I assuming possibly a back-packing trip??
What you MIGHT consider doing is taking a package trip. Look at AA.com and their vacation link .. they may have some good options. THEN book extension with the trip .. say make the whole trip to Germany (thru the tour company getting your air and hotel in Germany). Then pickup rail passes or intra EU flights to get to your other desired locataions. At the end of the month end up back where the flight goes from (Germany in my example). Be VERY aware that 'open jaw' might prove expensive (DFW-Manchester and then Rome to DFW would be an open jaw).
I'm not trying to discourage this but you are LATE in planning for the cheap fares!
Try using dream map where price is your key
http://dps1.travelocity.com/dreamMap...ce=TRAVELOCITY
I tried your proposed travel dates....with no regard to airline preference
MAN 873
LON (both) 852
FRA 959
AMS 901
PAris 1011
Rome 1124
MAD 928
Glasgow 1157
Birmingham 1097
Going a day shorter (31 vs 30) seems to have no impact.. its my assumption that height of summer will be the problem.
I also looked at a 5 night in London 'vacation' thru aa.com with flight and hotel using the 7/17 departure date. It comes out to about $1800 in a low-medium hotel .. so there is not a huge saving.
You may look into student group tours or other charters ... but for the regular airlines . this is probably as LOW as you'll find for these PEAK travel periods.
Good luck!
PS - I had to bite the bullet too on a Minneapolis to NY (then cruise to europe) and London back to minneapolis flight for August of over $1200.